U.S. Attorney General William Barr deserves to be impeached over the firing of a federal prosecutor whose office had been investigating President Donald Trump's personal lawyer but the effort would be a "waste of time," a leading Democratic lawmaker said on Sunday.

Jerrold Nadler, the House of Representatives Judiciary Committee chairman who helped lead the Trump impeachment hearings last year, told CNN's "State of the Union" that the Republican-led Senate would block any effort to sanction Barr.

"He certainly deserves impeachment. But again, that's a waste of time because the Republicans in the Senate won't look at that," Nadler said.

The firing of Geoffrey Berman, the U.S. attorney for the Southern District of New York, was the latest in a series of moves by Barr that critics say aim to benefit Trump politically and undermine the independence of the Justice Department.

Nadler's Sunday comments underscore the challenges Democrats face in trying to rein in Barr with a Senate dominated by Republicans who are wary of criticizing Trump before the November 3 presidential election.

Nadler said his panel would nonetheless investigate Trump's firing of Berman on Saturday after an extraordinary standoff over the independence of one of the country's most important federal prosecutor's office.

Berman has not shied from taking on figures in Trump's orbit and had been investigating his private lawyer, Rudy Giuliani.

U.S. Representative Adam Schiff, the lead prosecutor in Trump's impeachment, told NBC's "Meet the Press" the motivation for firing Berman was suspect, "given the pattern and practice of both the president in seeking to use the justice system to reward friends, punish enemies, protect people he likes, and Bill Barr's willingness to carry that water for the president."

Nadler said he was "sure" Berman would at some point testify in his committee's investigation of political interference at the Justice Department launched earlier this year.

The dispute began late Friday when Barr announced Berman was stepping down and would be replaced by U.S. Securities and Exchange Commission Chairman Jay Clayton, prompting Berman to issue a statement saying he refused to resign.

Only after Barr backtracked from his plan to hand pick the acting U.S. attorney, allowing Berman's deputy Audrey Strauss to take the reins, did Berman agree to step down on Saturday.

Some Democratic lawmakers, including Senator Elizabeth Warren, have called for Barr's impeachment. The Senate, where Republicans hold 53 of 100 seats, would never vote for that so the Democrat-led House would have to pursue alternative measures, Nadler said, citing his proposal to cut 50 million U.S. dollars in funding from Barr's personal budget.

In an email to SEC staff on Sunday, Clayton said he had pursued the role at the Southern District of New York because he had a "strong desire to continue in public service" while returning to New York where his family is based.

He also indicated that he had no intention of crossing the Trump administration by voluntarily removing himself from the process, as several Democrats including Senate minority leader Chuck Schumer had urged him to, telling staff he would update them when he had more information about his confirmation.