U.S. President Donald Trump's envoy for the Ukraine conflict met President Volodymyr Zelenskiy in Kyiv on Thursday but there was no immediate word on whether their talks had helped smooth over an unprecedented wartime rift between the once firm allies, and key U.S. officials indicated that major frustrations remain.

The Trump administration had earlier announced it had agreed to hold additional talks with Russia to end the nearly three-year-long conflict, following a 4.5-hour meeting in Saudi Arabia.

For the last three years, China has repeatedly signalled a willingness to act as a peacemaker in the war in Ukraine. There were rounds of shuttle diplomacy by Beijing's envoy to countries from South Africa to Indonesia.