Zelensky's visit to London followed his trip to Berlin, Germany, where on Wednesday he met with European leaders -- and spoke virtually with Trump -- to hammer out Ukraine's key demands in any peace negotiations to end Moscow's full-scale invasion, which began in February 2022.

British Prime Minister Keir Starmer is expected to welcome Ukrainian President Volodymyr Zelenskyy in London Thursday morning, the latest meeting between the Ukrainian leader and the head of a European country as the continent braces for a critical U.S.-Russia summit in Alaska on Friday.