Diplomats say there is an outside possibility that Trump might instead strike a unilateral deal with Putin, prioritising lucrative energy contracts and potential arms control accords. Trump himself has said he might conclude in Alaska that a Ukraine peace deal cannot be done.

President Trump has made a second-term push for a Nobel Peace Prize, but his Friday summit with Vladimir Putin could dent in his efforts.

Small bands of Russian soldiers thrust deeper into eastern Ukraine on Tuesday ahead of a summit this week between Russian President Vladimir Putin and U.S. President Donald Trump, which European Union states fear could end in peace terms imposed on an unlawfully shrunken Ukraine.