AP  Washington

Ukraine's future could hinge on a hastily assembled meeting on Monday at the White House as President Volodymyr Zelenskyy brings an extraordinary group of European leaders to show US President Donald Trump a united front against Russia.

The European leaders were left out of Trump's summit with Russian President Vladimir Putin last Friday, and they want to safeguard Ukraine and the continent from any widening aggression from Moscow. Many are coming with the explicit goal of protecting Ukraine's interests – a rare and sweeping show of diplomatic force.

By coming as a group, they hope to avoid debacles like Zelenskyy's February meeting in the Oval Office, where Trump chastised him for not showing enough gratitude for US military aid. Trump and Zelenskyy were due to meet in the Oval Office before European leaders join them in the East Room for talks.

The night before the meeting, however, Trump seemed to put the onus on Zelenskyy to agree to concessions and suggested that Ukraine could not regain Crimea, which Russia annexed in 2014, setting off an armed conflict that led to its broader 2022 invasion. 

"President Zelenskyy of Ukraine can end the war with Russia almost immediately, if he wants to, or he can continue to fight," Trump wrote Sunday night on social media. "Remember how it started. No getting back Obama given Crimea (12 years ago, without a shot being fired!), and NO GOING INTO NATO BY UKRAINE. Some things never change!!!"

Zelenskyy appeared to respond with his own post late Sunday, saying, "We all share a strong desire to end this war quickly and reliably." He said that "peace must be lasting," not as it was after Russia seized Crimea and part of the Donbas in eastern Ukraine eight years ago, and "Putin simply used it as a springboard for a new attack."