President Donald Trump said he will nominate William Barr as the next U.S. attorney general, putting an advocate of a strong executive branch in charge of the Justice Department as Special Counsel Robert Mueller’s Russia investigation intensifies.

Barr, if confirmed by the Senate, will take over after Jeff Sessions was ousted but the process could take several months.

"Hopefully that process will go very quickly," Trump said Friday at the White House. He, along with Acting Attorney General Matthew Whitaker, were traveling to Kansas City, Missouri, for a law enforcement event.

Senate Intelligence Chairman Richard Burr, a North Carolina Republican, said he knows Barr and he would be “a great pick.” Two Judiciary Committee Democrats —Amy Klobuchar of Minnesota and Chris Coons of Delaware —said Barr would have to commit to protecting Mueller’s probe.

Senator Susan Collins, a Maine Republican, said she would want to "make sure" Barr would allow Mueller to do his job and make sure that investigations at the Justice Department are independent.

Barr was attorney general from 1991 to 1993 under President George H.W. Bush, whose state funeral was Wednesday. As Bush’s top law enforcement official, he directed the investigation of the Lockerbie bombing, in which Pan Am Flight 103 was destroyed by terrorists connected to Libya, and led counter-terrorism efforts during the first Persian Gulf War, according to his biography at Kirkland & Ellis, where he’s now a lawyer.

Barr spent 15 years in telecommunications, joining joining GTE in 1994 and staying on after it merged with Bell Atlantic to become Verizon Communications. He served at the Central Intelligence Agency from 1973 to 1977 and was a political appointee at the Justice Department from 1989 to 1991 before his nomination to the department's top post.

As attorney general, Barr supported the six pardons that Bush issued related to the Iran-Contra scandal, including one for former Defense Secretary Casper Weinberger.

"I went over and told the president I thought he should not only pardon Caspar Weinberger, but while he was at it, he should pardon about five others," he recalled in 2001 interview for an oral history of the Bush presidency at the University of Virginia's Miller Center.

He mostly drew a hard line on crime and incarceration, arguing that the U.S. should build more prisons.

"Ask many politicians, newspaper editors, or criminal justice 'experts' about our prisons, and you will hear that our problem is that we put too many people in prison," the Justice Department said in a report published under Barr in 1992. "The truth, however, is to the contrary; we are incarcerating too few criminals, and the public is suffering as a result."

In 2015, he opposed retroactive reductions of prison sentences, writing in a letter to Senate leaders with other DOJ officials that a bill to reduce sentences would "benefit dangerous criminals" now imprisoned and make them "eligible for early release."

In his private practice, Caterpillar Inc., the iconic mining- and construction-equipment maker, hired Barr to lead a "fresh look" at the company's tax dispute with the Internal Revenue Service.

Barr was hired in 2017 after the IRS and other federal agencies raided the company's headquarters as part of a criminal investigation into whether the company illegally used a Swiss unit to avoid U.S. taxes. The company said in an Oct. 31 filing that it's cooperating with an ongoing grand jury investigation.

After an examination, the IRS has proposed back taxes and penalties of $2.3 billion, which the company is "vigorously contesting," according to the filing. Barr previously declined to comment on his role in the tax dispute.

Trump never forgave Sessions, the former Alabama senator, for recusing himself from supervising Mueller's probe, an investigation the president has repeatedly belittled as a "witch hunt."

Barr has criticized Mueller for hiring attorneys for his team who contributed to Democratic politicians, including Hillary Clinton.

"In my view, prosecutors who make political contributions are identifying fairly strongly with a political party," Barr told the Washington Post in July. "I would have liked to see him have more balance on this group."

Barr has also written that former FBI Director James Comey was right to publicly announce, days before the 2016 election, that he was re-opening an investigation of Hillary Clinton's handling of her emails as Secretary of State. He's also written that Trump was right to fire Comey as well as former Acting Attorney General Sally Yates.

Trump has came under criticism by members of Congress for naming Whitaker, Sessions’s chief of staff, as the acting attorney general instead of Deputy Attorney General Rod Rosenstein. Rosenstein appointed Mueller following Sessions’s recusal, a decision that angered the president.

Bloomberg’s Steven T. Dennis, Laura Litvan and David Voreacos contributed.