US President Barack Obama (left) and Polish President Bronislaw Komorowski speak with Polish and US soldiers at the military airport in Warsaw, Poland, on Tuesday. Obama is in Poland to meet regional leaders and attend ceremonies marking 25 years of Poland's democracy. Picture: Alik Keplicz

Warsaw - United States President Barack Obama landed in Poland on Tuesday at the start of a four-day trip to Europe meant to reassure allies there that the United States has their backs in the wake of the Russian intervention in Ukraine.

In Poland, Ukraine's western neighbour and a US Nato ally, Obama meets with leaders including Ukraine's president-elect, Petro Poroshenko, and is expected to address criticism he has not done enough to push back against Moscow after it annexed Crimea in March.

Obama began his day by meeting Polish President Bronislaw Komorowski at Warsaw airport. The two leaders will visit US and Polish airmen and are slated to appear a joint press conference after holding talks.

During brief remarks after his arrival, Obama said US commitments to Poland and the region were a cornerstone of the United States' own security. “As friends and allies we stand united together,” Obama said.

Later, Obama will meet Prime Minister Donald Tusk, followed by a session with other central and eastern European leaders who are gathered in Warsaw.

His visit coincides with the “Freedom Day” anniversary in Poland, which marks the holding of the country's first partially-free elections 25 years ago.

Later in the week, Obama travels to Brussels for a meeting of G7 leaders and then to France for the commemoration of the 70th anniversary of the D-Day landings in World War 2. - Reuters