Ukraine and its European allies have been buoyed by Donald Trump's promise of security guarantees for Kyiv to help end the war in Ukraine but face many unanswered questions, including how willing Russia will be to play ball. Volodymyr Zelenskiy hailed Monday's extraordinary summit at the White House with the U.S. president as a "major step forward" towards ending Europe's deadliest conflict in 80 years and towards setting up a trilateral meeting with Russia's Vladimir Putin and Trump in the coming weeks. But Academy associate for the Ukraine Forum at Chatham House, Olga Tokariuk, says the position of U.S. President Donald Trump can be manipulated and that he still sees Russia as a potential partner.