Acting White House chief of staff Mick Mulvaney said on Sunday he had not offered to resign for indicating last week that U.S. President Donald Trump had sought a political favor from Ukraine in exchange for military aid, comments he has since retracted.

"I never said there was a quid pro quo because there isn't," Mulvaney told Fox News Sunday, using a Latin phrase meaning a favor for a favor.

Mulvaney told reporters on Thursday that Trump's decision to withhold $391 million in aid to Ukraine was linked in part to his desire for an investigation by Kyiv into a debunked theory that a Democratic National Committee (DNC) computer server was held in Ukraine. His remarks at a White House news conference created turmoil in Washington and left the president's Republican allies flummoxed and frustrated.