(Reuters) -Ukrainian President Volodymyr Zelenskiy acknowledged on Wednesday that peace talks in London had been marked by "emotions" and pledged that Ukraine would abide by its constitution, an oblique reference to U.

U.S. President Donald Trump accused Ukraine's President Volodymyr Zelensky of jeopardizing peace talks to end the war because the European nation would never recognize Russia's occupation of the Crimean Peninsula.

Ukraine's leader ruled out the idea of ceding territory to Russia in any deal before talks set for Wednesday in London among US, European, and Ukrainian officials.

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.

London talks aimed at securing a ceasefire between Ukraine and Russia have been downgraded and will no longer include US Secretary of State Marco Rubio and special envoy Steve Witkoff. The meeting on Wednesday will instead take place among senior officials from the UK,

The Biden administration sought evidence of alleged Russian war crimes in Ukraine. The Trump administration is reportedly undoing those efforts.

However, Ukraine must first lift its ban on direct negotiations with Moscow. It follows the Trump administration making clear that it will walk away from trying to broker peace between Russia and Ukraine unless progress is made within days.

By Doina Chiacu, Elizabeth Piper and John Irish WASHINGTON/LONDON/PARIS (Reuters) -U.S. President Donald Trump and Ukrainian President Volodymyr Zelenskiy clashed again on Wednesday on efforts to end the three-year-old war in Ukraine,