Diplomats from the United States, Russia, Ukraine and the European Union have agreed to a framework plan designed to end violence in Ukraine.
Secretary of State John KerryJohn KerryFormer Obama officials say Netanyahu turned down secret peace deal: AP How dealmaker Trump can resolve the Israeli-Palestinian conflict John Kerry to teach at Yale on global issues MORE said the framework hashed out by foreign ministers meeting in Geneva would disarm separatist militants in eastern Ukraine and have them vacate the government buildings, streets and squares they have occupied.
The Ukrainian government has also "committed to going as far as they can to reach out to opponents" as part of a "comprehensive, inclusive process" ahead of next month's elections.
That will include consideration of constitutional amendments that could give Ukraine's Eastern regions greater autonomy.
President Obama expressed optimism that the framework was a positive step, but he acknowledged it was unclear whether separatists on the ground would follow through.
"We're not going to know whether in fact they'll follow through on these statements for several days," he said at a White House press conference.
Kerry agreed the agreement is a "good day's work," he said leaders understood that, so far, it's only "words on paper."
Obama and Kerry have repeatedly accused Russia of stirring up unrest in Ukraine, and they said they would hold Russia accountable if things did not improve. The president specifically suggested tougher sanctions could be imposed.
"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. "We have to be prepared to potentially respond to what continue to be efforts at interference."
Some outside observers raised questions about whether the agreement would really commit Russia to much of anything.
"There is no place for that, and unanimously every party joined today in its condemnation of that behavior," Kerry said.
Kiev also announced new restrictions on Russian citizens who wanted to cross the border into the country.
Russian airline Aeroflot told The Associated Press that Ukraine had informed the carrier that Russian men ages 16 to 60 were banned from entering the country unless they were traveling with family or to a funeral within the country.
"This applies to Russian citizens because there is information about possible provocations at the border, up to and including terrorist attacks," said Oleh Slobodian, a spokesman for the government in Kiev, according to Reuters. "Attention will be primarily paid to men of an active age, traveling alone or in a group."
Earlier Thursday, Russian President Vladimir Putin warned that the Ukrainian government's crackdown against protesters represented a "grave crime."
"I hope that they are able to realize what a pit, what an abyss the current authorities are in and dragging the country into," said Putin during an appearance on a call-in show.
The Russian leader also pointedly noted that he had been granted "the right to use military force in Ukraine."
"I really hope that I do not have to exercise this right and that we are able to solve all today's pressing issues via political and diplomatic means," Putin said.
Earlier Thursday, Defense Secretary Chuck Hagel said that the U.S. planned to offer additional non-lethal aid for the Ukrainian military, including helmets, sleeping mats and water purification systems.
"Earlier this morning I called Ukraine's acting defense minister to tell him that President Obama has approved additional non-lethal military assistance for health and welfare items and other supplies," Hagel said at a news conference.
This story was updated at 4:30 p.m.
Erik Wasson contributed to this story.