So as deputy attorney general, Rosenstein would have the power to remove Mueller from his position - as long as he had a good reason to do that and put it in writing.
Mueller was appointed on May 17 by the Justice Department as special counsel overseeing the investigation into Russia's alleged meddling in the 2016 U.S. elections and related matters.
In a letter sent to both committee chairs, Sessions said that he would send Rosenstein to the appropriations hearings, since "some members [of the committees] have publicly stated their intention to focus their questions on issues related to the investigation into Russian interference in the 2016 election, from which I have recused".
"The chain of command for the special counsel is only directly to the attorney general - and in this case, the acting attorney general", he said.
Rosenstein said that, under the special counsel regulations, he is the only department official with the authority to get rid of Mueller.
Sanders said Trump saw part of Sessions's testimony and "thought that Attorney General Sessions did a very good job and, in particular, was very strong on the point that there was no collusion between Russian Federation and the Trump campaign".
He said Attorney General Jeff Sessions is not involved in the Russian Federation probe and has not been briefed on it since his recusal.
Conservative commentator Ann Coulter offered a similar message, tweeting, "Now that we know TRUMP IS NOT UNDER INVESTIGATION, Sessions should take it back & fire Mueller". The regulations governing independent investigations make clear that the special counsel can be removed "only by the personal action of the Attorney General". "And the next day, he's now maybe using some of that information in his investigation". If accurate, the report would also indicate Trump still has no understanding of the position the appointment of a special counsel has placed him in. Democrats and millions of Americans won't buy it, but Mueller's reputation would be hard to question and that could put an end to it.
Firing Comey and then Mueller would leave Trump with the reputation of a man who will keep dismissing anyone serious about conducting an honest investigation.
Ruddy did not dismiss the White House communications team's words, but he did call Spicer's statement "bizarre". Congressman Paul Ryan, Speaker of the House of Representatives, said he has "confidence" in Mueller. The person spoke on condition of anonymity to discuss private conversations.
White House correspondent April Ryan, of American Urban Radio Networks, went on CNN on Monday night and told host Erin Burnett that there is "mass hysteria" in the White House over the possibility of firing the former Federal Bureau of Investigation director.