U.S. President's National Security Advisor John Bolton has expressed support for Ukraine in terms of the country's integrity.

During U.S. Vice President Mike Pence's meeting with Ukrainian President Zelensky, the U.S. Vice President’s message "couldn't have been more clear: the US has stood, and will continue to stand, with the people of Ukraine on their security and territorial integrity," John Bolton tweeted on Monday.

As UNIAN reported earlier, Zelensky and Pence met in Warsaw, Poland, where they arrived to take part in commemoration events marking the anniversary of the start of World War 2.

During the official visit, Zelensky also met with Polish and Lithuanian leaders.

With Mike Pence, the Ukrainian president discussed his upcoming visit to the U.S. where he is set to meet with his American counterpart, Donald Trump.