BRUSSELS — Russian President Vladimir Putin should prove he is committed to peace in Ukraine and stop supporting separatists, U.S. Secretary of State John Kerry said on Wednesday.

"We believe it is critical for President Putin to prove by his actions, not just his words, that he is indeed fully committed to peace," Kerry told a news conference following a NATO meeting of foreign ministers.

"It is critical for him to stop the flow of weapons and fighters across the border, to call publicly for the separatists to lay down their arms, to pull Russian forces and equipment back and to help get OSCE hostages released," he added.