FILE PHOTO: U.S. Senator Mitt Romney (R-UT) is pursued by reporters in the Senate subway as he arrives for the fourth day of the Senate impeachment trial of U.S. President Donald Trump at the U.S. Capitol in Washington, U.S., January 24, 2020. REUTERS/Erin Scott

WASHINGTON (Reuters) - U.S. Republican Senator Mitt Romney said on Monday that it was “increasingly likely” at least four Republican senators would join Democrats in calling for John Bolton, the former White House national security adviser, to testify in the Senate impeachment trial of U.S. President Donald Trump.

The New York Times cited an unpublished manuscript by Bolton that said Trump told him he wanted to freeze security aid to Ukraine until its officials helped probe Democrats, including Joe Biden, the former U.S. vice president and one of the candidates seeking the 2020 Democratic presidential nomination.

“I think it’s increasingly likely that other Republicans will join those of us who think we should hear from John Bolton,” Romney told reporters when asked if four Republicans might break ranks to support Democrats in their call for trial witnesses.