WASHINGTON — Deputy Attorney General Rod Rosenstein told members of a Senate appropriations subcommittee that he is the only person who is able to fire special counsel Robert Mueller and that he has seen no reason to do so.

The top Justice Department official overseeing the investigation into Russia also assured senators that Mueller has been granted complete independence to do his work.

Supporters of President Donald Trump floated the idea Monday that Trump should fire Mueller, and Chris Ruddy, a Trump confidant, told reporters after leaving the White House yesterday that Trump was considering doing just that.

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Rosenstein appointed Mueller last month to lead the investigation into Russian meddling in last year's election and potential Trump campaign ties to that effort.

He told senators during a committee hearing that there would have to be “good cause” for Mueller to be removed from his role. When asked by Sen. Jeanne Shaheen, D-N.H., if he’s seen any reason for Mueller to be fired, Rosenstein said, “I have not.”

Sen. Susan Collins, R-Maine, asked Rosenstein if he would fire Mueller if Trump asked him to.

“I’m not going to follow any orders unless they are a lawful order,” Rosenstein responded. The deputy attorney general also said: “I’m confident (Mueller) has full independence.”

Rosenstein is appearing before the appropriations subcommittee that oversees the Department of Justice’s budget because Attorney General Jeff Sessions cancelled his scheduled appearance after agreeing to appear before the Senate Intelligence Committee Tuesday. Sessions is set to discuss the scope of his recusal from the Russian investigation, any meetings he had with Russian officials as a surrogate of the Trump campaign and the circumstances around the firing of FBI Director James Comey.

Democratic senators on the committee attempted to clarify the boundaries of Sessions’ recusal, something they say is unclear.

“I know what we’re investigating and (Sessions) does not,” Rosenstein said, trying to clarify Sessions’ role. Unsatisfied, Sen. Brian Schatz, D-Hawaii, said that he’d like the scope in writing.

Related: As Sessions Set to Testify, What’s at Stake in Russia Probe?

Rosenstein continued to defend the investigation and the Department of Justice’s oversight, saying “I can assure you we’re going to do the right thing and defend the integrity of the investigation.”

Sen. Lindsey Graham, R-S.C., raised questions regarding Mueller’s independence, however. He said that campaign donations to Democrats don’t present a conflict of interest but that previous work with the Clinton Foundation and for the Clintons might.

“You can raise those concerns” to both Mueller and the DOJ, Rosenstein told Graham.