WARSAW, Feb. 21 (Xinhua) -- Visiting U.S. President Joe Biden on Tuesday called his country's relations with Poland "critical" and praised the Polish people for welcoming Ukrainians into their country.

During a bilateral meeting with his Polish counterpart, Andrzej Duda, Biden said that the United States needs Poland just as Poland needs the United States, according to a statement from the White House.

Duda said that Biden's visit is an important "sign of security", according to the Polish Press Agency.

Both leaders gave speeches on Tuesday afternoon on the eve of the first anniversary of the Russia-Ukraine conflict.

Biden vowed that his country and its allies "will not tire" of supporting Ukraine and emphasized the U.S. commitment to the North Atlantic Treaty Organization's (NATO) collective security, while Duda called on European nations and NATO to show solidarity with Ukraine.

Biden visited Poland after his surprise trip to Kiev on Monday. It was his second visit here in less than a year. He will also join a group of nine NATO member states located on the eastern flank of the bloc for the Bucharest Nine summit to be held here on Wednesday.