Washington, Feb. 17 -- Americans want Ukraine to return their investments in order to be comfortable with future spending, US National Security Adviser Michael Waltz has said.

"I can't think of anything that would make the American people more comfortable with future investments than if we were able to be in a partnership and have the American people made whole," he told Fox News in an interview aired Sunday.

Waltz argued that the European aid to Kiev came in the form of a loan backed by interest paid on Russian assets. He insisted that Americans, too, deserved to have "some type of payback" for the billions they had invested in Ukraine.

Waltz promised that the Europeans' opinion on the conflict would be taken into account during negotia...