"The United States remains firmly committed to Ukraine's sovereignty and territorial integrity, and that includes Crimea," Kerry told Lavrov at a meeting in the Kremlin in Moscow on Thursday, March 24.

Kerry also stressed the importance of the full implementation of the Minsk agreements concluded to restore peace in Donbas, eastern Ukraine.

"As President Obama reiterated in his recent call with President Putin, and as I underscored in our meeting today, our position is clear and we agree with Sergey Lavrov and Russia that the Minsk agreements must be fully implemented without delay," he said.

"We discussed how to get back to a real and comprehensive ceasefire and how to restore unfettered access for OSCE monitors and how to accelerate the process of a negotiated – of negotiating the election modalities for Donbas, which are all critical next steps in this journey," Kerry added.

In his words, the full implementation of the Minsk agreement is a major condition for lifting anti-Russian sanctions.

"I reinforced President Obama's pledge to roll back sanctions when all of the provisions of Minsk are complete, including the withdrawal of all weapons and fighters and the return of Ukraine's sovereign border," he said.

The parties also discussed the case of Ukrainian captive pilot Nadia Savchenko, who has recently been sentenced by a Russian court to 22 years in prison.

"Finally, I did raise the case of Nadia Savchenko and her conviction and her sentencing with hopes that she will be allowed to return to Ukraine and as a matter of humanitarian interest that this case could be resolved immediately, as well as all others who are unlawfully detained," Kerry said.