U.S. Secretary of State John Kerry will travel to London to meet with his Russian counterpart Sergei Lavrov on Friday, March 14, to try to ease tensions over Ukraine ahead of a referendum in its Crimea region on Sunday.

"President Obama has asked me to leave tomorrow evening and fly to London to meet with Russia's Foreign Minister Sergei Lavrov on Friday and I will do that," Kerry told the House Appropriations Committee on Foreign Operations on Wednesday, according to Reuters.

"Our job is to present them with a series of options that are appropriate in order to try to respect the people of Ukraine, international law, and the interests of all concerned," he said.