"Russia has a simple choice: fully implement Minsk or continue to face economically damaging sanctions," he said at the Munich Security Conference in Germany.
"Sanctions are never an end in and of themselves," Kerry said.
"But we shouldn't forget why they were imposed in the first place: to stand up for Ukraine's fundamental rights -- its sovereignty and territorial integrity.
"Put plainly, Russia can prove by its actions that it will respect Ukraine's sovereignty, just as it insists on respect for its own," he said.
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"The path to sanctions relief is clear: withdraw weapons and troops from Donbass, ensure that all Ukrainian hostages are returned, allow full humanitarian access to occupied territories, support free, fair, and internationally-monitored elections in Donbass under Ukrainian law, and restore Ukraine's control of its side of the international border."
Kerry praised European governments for "showing resolve and common purpose in the face of Russia's repeated aggression".
"I am confident that Europe and the United States will continue to stand united -- both in sustaining sanctions for as long as they are necessary and providing needed assistance to Ukraine."
"Almost every day we are accused of making new horrible threats either against NATO as a whole, against Europe or against the US or other countries," said Medvedev.