U.S. President Donald Trump could offer NATO-like protection of Ukraine, and Russia is open to the idea, one of his top foreign policy officials said on Sunday ahead of a meeting with Ukraine and European leaders to hammer out details of possible security guarantees for Kyiv.

Special U.S. envoy Steve Witkoff says Russian leader Vladimir Putin agreed to allow the U.S. and Europe to offer Ukraine a security guarantee resembling NATO's collective defense mandate.

Trump has signalled that Ukraine must accept Russia's terms on Crimea and NATO as Zelenskyy and top European leaders arrive at the White House for high-stakes talks.