Vice President Mike Pence has assured Ukraine's president his country has US support after President Donald Trump advocated for letting Russia re-join the Group of Seven despite its annexation of Ukraine's Crimea Peninsula.

Pence met with Ukrainian President Volodymyr Zelenskiy after observances marking the start of World War II 80 years ago in Poland. They talked in the wake of Trump's comments and his administration's decision to hold up $250 million in security aid to Ukraine.

Pence said the United States had ``stood strongly for the territorial integrity of Ukraine'' when Russia seized Crimea in 2014. Ukraine and most other nations see the move as illegal.

He added: "We will continue to stand with the people of the Ukraine on your security, on territorial integrity, including the Ukraine's rightful claim to Crimea.''