The fast-moving developments in Trump's near-back-to-back summits with the heads of Russia, Ukraine and European powers have highlighted a pair of repeated sticking points.

Ahead of his meeting with European leaders Monday, Trump put pressure on Ukrainian President Volodymyr Zelenskiy to end the invasion of his own country by handing over seized territory and dropping his dreams of belonging to the powerful military alliance.

"I like the concept of a ceasefire for one reason, because you'd stop killing people immediately... But we can work a deal where we're working on a peace deal while they're fighting." President Trump walked back on his previous comments where he suggested "severe consequences" for Russia if Russian President Vladimir Putin didn't agree to a ceasefire before a meeting with Ukrainian President Volodymyr Zelenskyy and other European and NATO leaders.