"They're having a meeting in Munich tomorrow. Russia's going to be there with our people. Ukraine is also invited, by the way. Not sure exactly who's going to be there from any country, but high-level people from Russia, from Ukraine and from the United States," Trump told reporters.

When asked for further details, the White House declined comment.

"Ukraine has so far no knowledge of this beyond the media," said a Ukrainian source, speaking on condition of anonymity. "As of now, no-one has heard."

Russia's embassy in Washington and mission to the United Nations in New York did not immediately respond to requests for comment.