Obama says the U.S. has done everything possible to support Ukraine's government and to deter Russia. But he says short of going to war, there are going to be constraints about what the U.S. can do.
Obama says the U.S. is imposing sufficient costs, and Russia should want to take the needed steps to get economic sanctions lifted.
But Obama says, quote, "people don't always act rationally." He says sometimes people don't act based on their own interests.
Obama says the U.S. must keep working to de-escalate the conflict.