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., Ukrainian and European officials held "substantive" meetings in London on Wednesday to try to revive peace talks after U.S. Secretary of State Marco Rubio canceled his trip, raising questions over how much progress was being made.

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.