Britain's new Prime Minister Boris Johnson gestures as he speaks outside 10 Downing Street, London, Wednesday, July 24, 2019. Boris Johnson has replaced Theresa May as Prime Minister, following her resignation last month after Parliament repeatedly rejected the Brexit withdrawal agreement she struck with the European Union. (AP Photo/Frank Augstein)

LONDON (AP) — Boris Johnson took over as Britain's prime minister Wednesday, vowing to break the impasse that defeated his predecessor by leading the country out of the European Union and silencing "the doubters, the doomsters, the gloomsters" who believe it can't be done.

But the brash Brexit champion faces the same problems that flummoxed Theresa May during her three years in office: heading a government without a parliamentary majority and with most lawmakers opposed to leaving the EU without a divorce deal.

Johnson has just 99 days to make good on his promise to deliver Brexit by Oct. 31 after what he called "three years of unfounded self-doubt."

He optimistically pledged to get "a new deal, a better deal" with the EU than the one secured by May, which was repeatedly rejected by Britain's Parliament.

"The people who bet against Britain are going to lose their shirts," he said, standing outside the shiny black door of 10 Downing St.

Trying to avoid the political divisions that plagued May, Johnson swept out many of her ministers to make way for his own team, dominated by loyal Brexiteers. He appointed Sajid Javid to the key role of Treasury chief, named staunch Brexit supporter Dominic Raab as foreign secretary and made Priti Patel the new home secretary, or interior minister. Michael Gove, who ran the 2016 campaign to leave the EU alongside Johnson, also got a Cabinet job.

Over half of May's Cabinet is gone, including ex-Foreign Secretary Jeremy Hunt, Johnson's defeated rival for the Tory leadership, who said he had turned down the chance to stay in government in a different job.

In his first speech as prime minister, Johnson unleashed a scattershot spray of promises — from more police on the streets to ending a ban on genetically modified crops to faster internet access.

To the many critics of the polarizing politician who find the phrase "Prime Minister Boris Johnson" jarring, it was typical of a verbal vim that is not always wedded to hard facts .

For the 55-year-old Johnson, walking into the Downing Street residence was the culmination of a life's ambition. The flamboyant, Latin-spouting former London mayor and foreign secretary helped lead the 2016 campaign to get Britain out of the EU and is now the darling of Brexit backers who feel frustrated that, three years later, the country is still in the bloc.

Judging by his words on Wednesday, Johnson's approach to the EU will be a mix of charm and threats.

He vowed to keep relations with the EU "as warm and as close and as affectionate as possible" and promised the 3 million EU nationals in Britain "absolute certainty" that they can stay. May made the same promise, but it still is not enshrined in law.

In the next breath, Johnson said Britain might be forced to leave with no deal if "Brussels refuses any further to negotiate" — trying to pin the blame for any future failure on the bloc. That's not an approach likely to win the trust and confidence of EU leaders.

The EU is adamant it will not renegotiate the agreement struck with May on the terms of Britain's departure and the framework of future relations. Without it, Britain faces a chaotic Brexit that economists warn would disrupt trade by imposing tariffs and customs checks between Britain and the bloc, send the value of the pound plummeting and plunge the U.K. into recession.

Chief EU Brexit negotiator Michel Barnier said "we are ready to listen and to work with" Johnson, but he did not budge on the bloc's refusal to alter the deal.

"A no-deal Brexit will never be, never, the choice of the EU. But we are prepared," he said in Brussels before Johnson spoke.

Johnson's political opponents accused him of offering little more than hot air.

"Rhetoric and reality are two different things," said Labour Party Brexit spokesman Keir Starmer.

Scottish First Minister Nicola Sturgeon tweeted that Johnson's speech was "rambling, blame-shifting and, to put it mildly, somewhat divorced from reality."

Wednesday's carefully choreographed political drama unfolded with May attending the weekly Prime Minister's Questions period in the House of Commons for the last time . The usually boisterous session was subdued, with Conservative colleagues praising May's sense of duty and opposition leaders offering best wishes.

As she left the chamber, May received a standing ovation from Conservative lawmakers, many of whom helped bring her down by rejecting her Brexit deal.

Later, she stood in Downing Street alongside her husband Philip and said it had been "the greatest honor" to serve as prime minister. She then went to Buckingham Palace to tender her resignation to Queen Elizabeth II.

Moments after her Jaguar left the palace, Johnson swept in to see the queen and be appointed the 14th prime minister of her 67-year reign. Her first was Winston Churchill, who is idolized by Johnson.

There was a brief hiccup in the smooth handover when Greenpeace climate-change protesters blocked Johnson's car by forming a human chain on the road outside the palace. They were quickly moved aside by his police escort. Later, hundreds of people demonstrated in central London against Johnson's support for Brexit and past offensive remarks about Muslims, women and others.

If he is to succeed, Johnson must win over the many Britons opposed to Brexit and resistant to his blustering charisma.

In a sign he hopes to move beyond the largely white, male and affluent Conservative members who chose him as their leader, Johnson's office said his government would be a "Cabinet for modern Britain" with more women and a record number of ministers from ethnic minorities.

His administration is also set to include some pro-EU politicians, but most will be strong Brexit supporters. One of his senior advisers is set to be Dominic Cummings, lead strategist for the 2016 referendum.

A contentious figure, Cummings was found to be in contempt of Parliament earlier this year for refusing to give evidence to a committee of lawmakers investigating "fake news."

British lawmakers are due to start a six-week summer break on Friday. When they return in September, Johnson looks set for a fight with lawmakers, a majority of whom oppose leaving the EU without a deal.

That has led to speculation he could call a snap election in hopes of gaining a majority in Parliament for his plans.

Political commentator Matthew Parris, a former Conservative lawmaker, said Johnson was about to find out whether the skills that have brought him to power would work in government.

"However far excitement, energy, positivity can take you ... they will take Boris Johnson that far," he said. "But there is a limit."

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Follow AP's full coverage of Brexit and the Conservative Party leadership race at: https://www.apnews.com/Brexit

Britain's Queen Elizabeth II welcomes newly elected leader of the Conservative party Boris Johnson during an audience at Buckingham Palace, London, Wednesday July 24, 2019, where she invited him to become Prime Minister and form a new government. (Victoria Jones/Pool via AP)
Britain's new Prime Minister Boris Johnson waves from the steps outside 10 Downing Street, London, Wednesday, July 24, 2019. Boris Johnson has replaced Theresa May as Prime Minister, following her resignation last month after Parliament repeatedly rejected the Brexit withdrawal agreement she struck with the European Union. (AP Photo/Frank Augstein)
Newly elected leader of the Conservative party Boris Johnson, center, arrives at Buckingham Palace in London for an audience with Queen Elizabeth II where he will be formally invited to become Prime Minister, Wednesday July 24, 2019. Boris Johnson will replace May as Prime Minister later Wednesday, following her resignation last month after Parliament repeatedly rejected the Brexit withdrawal agreement she struck with the European Union. (Yui Mok/pool via AP)
Young people take to the streets to oppose the election of the new British Prime Minister Boris Johnson in London, Wednesday, July 24, 2019. Boris Johnson has replaced Theresa May as Prime Minister, following her resignation last month after Parliament repeatedly rejected the Brexit withdrawal agreement she struck with the European Union. (AP Photo/Vudi Xhymshiti)
Britain's new Prime Minister Boris Johnson speaks outside 10 Downing Street, London, Wednesday, July 24, 2019. Boris Johnson has replaced Theresa May as Prime Minister, following her resignation last month after Parliament repeatedly rejected the Brexit withdrawal agreement she struck with the European Union. (AP Photo/Matt Dunham)
Carrie Symonds, partner of Britain's new Prime Minister Boris Johnson, applauds after his speech outside 10 Downing Street, London, Wednesday, July 24, 2019. Boris Johnson has replaced Theresa May as Prime Minister, following her resignation last month after Parliament repeatedly rejected the Brexit withdrawal agreement she struck with the European Union. (AP Photo/Tim Ireland)
Britain's Prime Minister Theresa May looks around as she speaks outside 10 Downing Street, London before leaving for Buckingham Palace where she will hand her resignation to Queen Elizabeth II, Wednesday, July 24, 2019. Boris Johnson will replace May as Prime Minister later Wednesday, following her resignation last month after Parliament repeatedly rejected the Brexit withdrawal agreement she struck with the European Union. (AP Photo/Frank Augstein)
Britain's Prime Minister Theresa May and her husband Philip waves from the steps of 10 Downing Street, London before leaving for Buckingham Palace where she will hand her resignation to Queen Elizabeth II, Wednesday, July 24, 2019. Boris Johnson will replace May as Prime Minister later Wednesday, following her resignation last month after Parliament repeatedly rejected the Brexit withdrawal agreement she struck with the European Union. (AP Photo/Frank Augstein)
Britain's Prime Minister Theresa May leaves 10 Downing Street, for the House of Commons to attend Prime Minister's Questions in London, Wednesday, July 24, 2019. Boris Johnson will replace May as Prime Minister later Wednesday, following her resignation last month after Parliament repeatedly rejected the Brexit withdrawal agreement she struck with the European Union. (AP Photo/Tim Ireland)
Britain's Prime Minister Theresa May, with her husband Philip May, leaves 10 Downing Street, London for Buckingham Palace, Wednesday, July 24, 2019. Boris Johnson will replace May as Prime Minister later Wednesday, following her resignation last month after Parliament repeatedly rejected the Brexit withdrawal agreement she struck with the European Union. (AP Photo/Matt Dunham)
Britain's new Chancellor Sajid Javid arrives at the treasury in London, Wednesday, July 24, 2019. British Prime Minister Boris Johnson has appointed Sajid Javid the country's new Treasury chief, one of the most senior jobs in Cabinet. Javid will be responsible for spending and economic policy in Johnson's government. (AP Photo/Matt Dunham)
Conservative lawmkaer Dominic Raab is seen at the Foreign and Commonwealth building after being appointed as the Foreign Secretary by new Prime Minister Boris Johnson, on Wednesday, July 24, 2019 in London. Dominic Raab has been named Britain's foreign secretary, the country's top diplomat and one of the most senior roles in government. Raab is a former Brexit secretary and a staunch supporter of Britain's exit from the European Union. (Dan Kitwood/Pool Photo via AP)
Britain's New Prime Minister Boris Johnson is welcomed into 10 Downing Street by staff, in London, Wednesday, July 24, 2019. Britain's new Prime Minister Boris Johnson has vowed the U.K. will leave the European Union on Oct. 31 —
Carrie Symonds the girlfriend of Britain's new Prime Minister Boris Johnson waits in 10 Downing Street, London, Wednesday, July 24, 2019. Boris Johnson has replaced Theresa May as Prime Minister, following her resignation last month after Parliament repeatedly rejected the Brexit withdrawal agreement she struck with the European Union. (AP Photo/Frank Augstein)