Ex-national security adviser John Bolton John BoltonJudge appears skeptical of Bolton's defense of publishing book without White House approval Maximum pressure is keeping US troops in Iraq and Syria Woodward book trails Bolton, Mary Trump in first-week sales MORE described President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE's personal attorney Rudy Giuliani Rudy GiulianiThe Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting CIA found Putin 'probably directing' campaign against Biden: report Democrats fear Russia interference could spoil bid to retake Senate MORE as a "hand grenade who's going to blow everybody up" in a private conversation with another official who was deposed by congressional committees on Monday as part of the impeachment inquiry.

Bolton made the comment to Fiona Hill, the senior director for Russian and Eurasian affairs, in a July 10 conversation after a separate meeting with Gordon Sondland, the Trump donor who became U.S. ambassador to the European Union, according to a report by The New York Times.

The Times was reporting on Hill's testimony to three committees on Monday, all of which was behind closed doors.

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The remarks attributed to Bolton, who previously worked in the administration of President George W. Bush, highlights the differences within the Trump administration over an effort to pressure Ukraine to investigate former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE, a leading candidate for the Democratic presidential nomination in 2020.

They also highlight tensions within the administration over the activities of Giuliani, the former New York City mayor who appeared to be running a shadow diplomacy effort with Ukraine.

After a testy exchange with Sondland on July 10, according to the Times, Bolton told Hill to alert White House lawyers about the pressure campaign officials were making on Ukraine to conduct an investigation into Biden.

“I am not part of whatever drug deal Rudy and Mulvaney are cooking up,” Bolton told Hill to tell White House lawyers, according to the testimony reported by the Times. That is a reference to Mick Mulvaney Mick MulvaneyOn The Money: House panel pulls Powell into partisan battles | New York considers hiking taxes on the rich | Treasury: Trump's payroll tax deferral won't hurt Social Security Blockchain trade group names Mick Mulvaney to board Mick Mulvaney to start hedge fund MORE, the acting White House chief of staff.

Hill said Bolton told her to contact the chief lawyer for the National Security Council about an effort by Sondland, Giuliani and Mulvaney, according to sources who spoke with the Times.

Hill testified for 10 hours behind closed doors on Monday as part of the impeachment inquiry into Trump.

The inquiry is centered on allegations that Trump asked Ukraine to investigate Biden and his son.

Sondland is also set to testify to Congress this week behind closed doors.

Bolton resigned as national security adviser in September after numerous differences with Trump.

Two associates of Giuliani were indicted last week on campaign finance charges related to an effort to get money to U.S. politicians and influence U.S. policy toward Ukraine.