In earlier talks with Polish President Bronislaw Komorowski, Obama urged Poland to help Ukraine and Belarus with democratic reforms.
Obama criticized Belarus for "backsliding" and a 'total disregard for democratic values.'
Belarus President Alexander Lukashenko has intensified a crackdown on the opposition, jailing presidential candidates, and kicking out foreign media for stirring up "hysteria" over the country's economic crisis.
On Friday, US officials announced that F-16 fighters would be rotated to a Polish base for training purposes, in a further deepening of military ties.
Obama also said he and Tusk had discussed nuclear and gas energy cooperation. America’s Westinghouse Corp. is in the running to help build Poland’s first nuclear reactor by 2020.
Shale gas drilling, or “fracking” as it is called, is facing mounting global criticism over fears the technique could pollute ground water, but not in Poland, where even Greenpeace has given its conditional support, saying it could help wean Poland off of its coal addiction.