WASHINGTON -- US President Donald Trump will meet Ukrainian leader Volodymyr Zelenskyy on the sidelines of this week's NATO summit in Ankara, the White House announced on July 5, as Washington seeks to revive stalled diplomacy over Russia's war while pressing Europe to take greater responsibility for the continent's defense.The announcement came a day after Trump held separate telephone conversations with Zelenskyy and Russian President Vladimir Putin, underscoring the administration's effort to position itself as the key mediator in a conflict that has entered its fifth year with no breakthrough in peace efforts.Following the call, Zelenskyy said he had briefed Trump on the battlefield situation and that the two leaders agreed to continue discussions during the NATO summit."There is a real prospect to put an end to this war, and America's resolve is decisive," Zelenskyy wrote on X.Zelenskyy also warned that intelligence suggests Russia is preparing yet another massive air campaign against Ukraine, following the deadly barrage on the night of July 1–2."This is in the spirit of Putin -- right after America's Independence Day and before the NATO summit in Ankara. Russia wants to add to the evil and kill people," Zelenskyy said in his video statement on July 5.The Kremlin said Trump's roughly 90-minute conversation with Putin included Trump's reiteration of his readiness to continue mediation efforts, while Putin repeated Moscow's position that any settlement must take account of Russia's "fundamental approach" to resolving the conflict.The calls come as months of US-led diplomacy have failed to narrow the gap between Kyiv and Moscow. Russia continues to insist on control of the occupied parts of Ukraine's east, while Kyiv has rejected territorial concessions.White House Says Battlefield Has Largely StalledWhite House Principal Deputy Press Secretary Anna Kelly confirmed that Trump would meet Zelenskyy on July 8.