His remarks, in Paris, came a day before a cease-fire in the restive Donetsk and Luhansk regions of eastern Ukraine was scheduled to end. Further European Union and U.S. sanctions could come if Russia makes no attempt to defuse the situation in Ukraine.
Separatist leaders in Donetsk and Luhansk have declared their territory independent, and Russian weaponry, including tanks, have been seen in the area. Russia has denied involvement in arming the separatists.
"It is critical for Russia to show in the next hours, literally, that they are moving to help disarm the separatists, to encourage them to disarm, to call on them to lay down their weapons and begin to become part of a legitimate political process," Kerry said.
Ukrainian President Petro Poroshenko, in Strasbourg, France, to address the parliament of the Council of Europe, said Russian President Vladimir Putin's response has thus far been "insufficient" and called on Putin to endorse Poroshenko's peace plan "with deeds, not words."
On Wednesday and Thursday, Putin held telephone conversations with Poroshenko, French President Francois Hollande and German Chancellor Angela Merkel. His talk with Merkel concerned the "need to extend the ceasefire," a Kremlin statement said.