President Barack Obama held a private meeting Wednesday with the new president of Ukraine.
President Petro Poroshenko, who was elected just 10 days ago, is vowing to retake parts of eastern Ukraine from pro-Russia separatists.
Obama is in Warsaw to help commemorate the 25th anniversary of Poland's first partially free election. He plans to point to Poland as an example of democratic progress for the people in neighboring Ukraine in a speech Wednesday.
"We stand together because we believe that people and nations have the right to determine their own destiny - and that includes the people of Ukraine," Obama told a crowd of more than 6,000 Polish residents Wednesday.
"Our free nations will stand united so that further Russian provocations will only mean more isolation and costs for Russia," he continued. "Because after investing so much blood and treasure to bring Europe together, how can we allow the dark tactics of the 20th century to define this new century?"
Meanwhile, the Ukrainian military is stepping up its offensive, with troops breaking through rebel held positions in the city of Slovyansk.
Government officials are warning residents in the city and surrounding areas to stay at home while they fight the insurgents.
That warning comes as a Christian orphanage in Slovyansk was attacked. The center is partially supported by CBN's Orphan's Promise.
No children were hurt in the attack, but Orphan's Promise has moved all the kids to a safe place in western Ukraine.