Obama: Ukraine deal 'promising,' but Russia must follow through

President Obama offered cautious optimism Thursday about a framework agreement designed to de-escalate the crisis in Ukraine, but warned the U.S. is ready to move forward with additional penalties if the situation on the ground does not improve.

"There was a promising public statement that indicated the need to disarm all irregular forces and militias and groups," Obama said of the deal announced earlier in the day by Secretary of State John Kerry.

But Obama cautioned that "we're not going to know whether in fact they'll follow through on these statements for several days."

"We have put in place additional consequences we can impose on the Russians if we do not see actual improvement on the ground," Obama said.

“My hope is that we actually do see follow-through over the next several days, but I don't think, given past performance, that we can count on that, and we have to be prepared to potentially respond to what continue to be ... efforts of interference by the Russians in Eastern and Southern Ukraine.”

A joint statement issued by the foreign ministers of the U.S., Russia, Ukraine, and the European Union called on pro-Russian separatists in Eastern Ukraine to vacate the government buildings, streets and squares they have occupied.

In return, the Ukrainian government has offered amnesty to pro-Russian militants, with the exception of those who committed capital crimes. Ukraine has also pledged to open up a review of its constitution, which will include consideration of amendments that could give Ukraine's eastern regions greater autonomy.

The U.S. and Europeans have also agreed to hold off on additional sanctions as the pro-Russian forces withdraw.

Obama said he hoped that domestic pressure on Russian president Vladimir Putin would help push Russia to comply with the agreement.

"This whole exercise by the Russians is not good for Russia either … an economy that was already stuck in the mud is further deteriorating because of these actions," Obama said.