US Secretary of State, John Kerry and Russian Foreign Minister Sergei Lavrov are due to hold crucial talks to try to ease tensions over the Ukraine crisis.

The US accuses Moscow of deploying troops in Ukraine's Crimea region, describing it as an act of aggression, a claim denied by the Kremlin.

Despite the sharp differences, both sides have hinted they would prefer to start a dialogue. Moscow remains in de facto control of Ukraine's southern autonomous region. The tense stand-off continued overnight in Crimea, but there were no reports of any violence.

Earlier this week, tensions escalated further over Russia's warnings that it could also move into eastern Ukraine to protect Russians and Russian-speakers there.