Denmark's Crown Princess Mary, left, and Crown Prince Frederik, second from left, welcome by Poland's President Andrzej Duda, second from right, and his wife Agata Kornhauser-Duda, right, during the welcoming ceremony at the start of their one-day visit marking 100 years of bilateral relations, in the Presidential Palace in Warsaw, Poland, Monday, Nov. 25, 2019. (AP Photo/Czarek Sokolowski)

WARSAW, Poland (AP) — Danish Crown Prince Frederik and Crown Princess Mary marked 100 years of Denmark’s diplomatic ties with Poland with a one-day visit to Warsaw Monday that involved meeting Poland’s president and World War II veterans.

Frederik and Mary were greeted with military honors by Polish President Andrzej Duda in front of the Presidential Palace.

Later in the day, they were set to open a conference at Warsaw University on the history of the countries’ ties.

They were also due at the nearby Polish Academy of Sciences to dedicate a memorial plaque to Danish 19th-century sculptor Bertel Thorvaldsen, who made a popular monument in Warsaw to Polish astronomer Nicolaus Copernicus.

They were also to lay a wreath at the Tomb of the Unknown Soldier and meet war veterans.

Talks in coal-reliant Poland were to include climate protection and a joint gas pipeline project, Baltic Pipe, to bring Norwegian gas to Denmark and Poland.

Denmark's Crown Princess Mary, left, and Crown Prince Frederik, second from left, welcome by Poland's President Andrzej Duda, second from right, and his wife Agata Kornhauser-Duda, right, during the welcoming ceremony at the start of their one-day visit marking 100 years of bilateral relations, in the Presidential Palace in Warsaw, Poland, Monday, Nov. 25, 2019. (AP Photo/Czarek Sokolowski)
Denmark's Crown Princess Mary, left, and Crown Prince Frederik, second from left, welcome by Poland's President Andrzej Duda, second from right, and his wife Agata Kornhauser-Duda, right, during the welcoming ceremony at the start of their one-day visit marking 100 years of bilateral relations, in the Presidential Palace in Warsaw, Poland, Monday, Nov. 25, 2019. (AP Photo/Czarek Sokolowski)
Denmark's Crown Prince Frederik, left, and Crown Princess Mary, second from left, welcome by, Poland's President Andrzej Duda, second from right, and his wife Agata Kornhauser-Duda, right, during welcoming ceremony at the start of their one-day visit marking 100 years of bilateral relations, in the Presidential Palace in Warsaw, Poland, Monday, Nov. 25, 2019.(AP Photo/Czarek Sokolowski)
Poland's President Andrzej Duda,left, and first lady Agata Kornhauser-Duda wait to receive Danish Crown Prince Frederik and Princess Mary, before welcoming ceremony at the start of their one-day visit that marks 100 years of bilateral relations, in the Presidential Palace in Warsaw, Poland, Monday, Nov. 25, 2019.(AP Photo/Czarek Sokolowski)
Poland's President Andrzej Duda,left, and first lady Agata Kornhauser-Duda wait to receive Danish Crown Prince Frederik and Princess Mary, before welcoming ceremony at the start of their one-day visit that marks 100 years of bilateral relations, in the Presidential Palace in Warsaw, Poland, Monday, Nov. 25, 2019. (AP Photo/Czarek Sokolowski)