The lawyer for Mick Mulvaney said the acting White House chief of staff had no knowledge that former national security adviser John Bolton had conversations with President Donald Trump where the president reportedly said he would withhold U.S. military aid to Ukraine in exchange for investigations into his political rivals.

The revelations of those conversations came from a manuscript of Bolton’s upcoming book. The manuscript’s contents were first reported on by The New York Times and later confirmed by the Associated Press.

Bob Driscoll, Mulvaney’s attorney, dismissed Bolton’s story in a statement sent to PBS NewsHour.

“The latest story from the New York Times, coordinated with a book launch, has more to do with publicity than the truth. John Bolton never informed Mick Mulvaney of any concerns surrounding Bolton’s purported August conversation with the President. Nor did Mr. Mulvaney ever have a conversation with the President or anyone else indicating that Ukrainian military aid was withheld in exchange for a Ukrainian investigation of Burisma, the Bidens, or the 2016 election.”

Read the statement from Mulvaney’s attorney

The revelation has increased pressure for senators to call witnesses in the impeachment trial of the president, which has centered around Trump’s call with the Ukrainian president. Senate Minority Leader Chuck Schumer on Monday called on Bolton to testify, following the release of the book draft.