Congressional Democrats, concerned about protecting Mueller, called on Whitaker to recuse himself from overseeing the investigation in its final but potentially explosive stages. Whitaker, who has been a critic of the Russia probe, now has the power to fire Mueller or curb his investigation into Russian interference in the 2016 presidential campaign. He said there was no evidence of collusion. He had frequently publicly castigated Sessions for recusing himself previous year from the case.
There has also been a question mark over Mr Rosenstein's future since it was alleged that he had discussed invoking a constitutional clause to oust President Trump.
In the letter, the group of state attorneys general note that Rosenstein appears to have adequately overseen the Russian Federation probe and "should continue to do so, as Mr. Mueller's work must proceed free from interference or supervision that would appear to many Americans to be biased".
Matthew Whitaker, 49, a Republican lawyer said to be a Trump loyalist, assumed oversight of the inquiry after the president promoted him from chief of staff to Jeff Sessions, who was sacked as attorney-general on Wednesday.
Mr Whitaker can now assume control of the Mueller inquiry, which has been overseen by Deputy Attorney General Rod Rosenstein until now.
Whitaker, who had a stint as a legal commentator for CNN, has been vocal in his criticism of Mueller's investigation and its scope.
Bondi has been a stauncher supporter of Trump during his campaign for the presidency and after taking office.
"The President has said on multiple occasions the Mueller investigation should be completed".
Trump said at the news conference that he wanted the Mueller probe to end, calling it "very unfair".
But there has also been speculation Mr Trump could try to kill or suppress the 18 month-old probe, pressing his view that Mr Mueller leads a team staffed by Democrats operating under an illegal mandate.
It is not clear how long Whitaker will be the acting attorney general, as a discussion about a permanent replacement is underway at the White House in the wake of Sessions' resignation.
Sessions endured the name-calling in silence, even as he aggressively carried out the administration's conservative policies, such as stripping federal funding from so-called sanctuary cities and states and rescinding protection for young adults brought into the country illegally as children.
Troubled that the president has crossed a "red line" toward firing special counsel Robert Mueller, more than 900 activists have planned protests on Thursday at 5 p.m. nationwide, including in Santa Barbara. Another person said that remained true ever after Whitaker took his place.