A major meeting in London aimed at bringing about an end to Russia’s war in Ukraine has been downgraded after US Secretary of State Marco Rubio said he would skip the summit, escalating a clash between Washington and Kyiv over the future of Russian-occupied Crimea.

Talks between the U.S., Ukraine and European officials to discuss ending Russia's war in Ukraine faltered as Secretary of State Marco Rubio abruptly cancelled his trip to London.

U.S. Secretary of State Marco Rubio will not attend talks in London aimed at ending the war in Ukraine, State Department spokesperson Tammy Bruce said on Tuesday, after earlier saying he planned to travel to London.