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 welcomed Ukrainian President Volodymyr Zelenskyy to London, a day before a critical U.S.-Russia summit in Alaska.