Update 12.50pm: Donald Trump is not considering sacking the special counsel investigating Russian election interference, a top White House lawyer said.
A cascade of tweets revived speculation the US president may be preparing to get rid of the veteran prosecutor.
The statement from White House lawyer Ty Cobb came after top congressional Republicans warned of repercussions if Mr Trump removed special counsel Robert Mueller, who is looking into contacts between the president's 2016 campaign and Russian meddling in the election.
In a series of weekend tweets, Mr Trump jabbed directly at Mr Mueller by name for the first time. The president challenged the investigation's existence and suggested political bias on the part of Mr Mueller's investigators.
The tweets revived talk that Mr Trump may, in an attempt to end the investigation, move to have Mr Mueller sacked. Mr Cobb sought to dampen down the speculation.
"In response to media speculation and related questions being posed to the Administration, the White House yet again confirms that the president is not considering or discussing the firing of the special counsel, Robert Mueller," he said.
On Sunday, members of US congress, including some top Republicans, warned Mr Trump not to even think about removing Mr Mueller.
"If he tried to do that, that would be the beginning of the end of his presidency," said senator Lindsey Graham, a Trump ally.
Earlier 8.07am: Donald Trump has signalled a possible shift away from a strategy of cooperating with the Russia probe he believes is biased against him.
The President on Sunday took out his frustrations over the intensifying investigation by lashing out at special counsel Robert Mueller.
The president has long been torn over how to approach Mr Mueller's probe.
Mr Trump insists that his campaign did not collude with Russia, and his legal team, namely attorney Ty Cobb, has counselled the president to cooperate with Mr Mueller.
But some former campaign advisers have urged Mr Trump to be combative, warning him that that the investigation poses an existential threat to his presidency.
Mr Cobb said late Sunday that Mr Trump is not thinking about or talking about firing Mr Mueller.
"In response to media speculation and related questions being posed to the Administration, the White House yet again confirms that the President is not considering or discussing the firing of the Special Counsel, Robert Mueller," Mr Cobb said in a written statement.
Mr Trump's attacks raised new concerns among members of Congress that he could be seeking to orchestrate Mueller's firing. Republican and Democratic lawmakers warned Trump to not even think about it.
In a series of weekend tweets naming Mr Mueller for the first time, Mr Trump criticised the investigation into Russian interference in the 2016 presidential election and raised fresh concerns about the objectivity and political leanings of the members of the counsel's team.
Mr Trump also challenged the honesty of Andrew McCabe, the newly fired FBI deputy director, and James Comey, the bureau's former director whom the president fired last year over the Russia probe.
Mr Trump's aggressive stance followed a call on Saturday by his personal lawyer for Rod Rosenstein, whom the president appointed as deputy attorney general and who now oversees Mr Mueller's inquiry, to "bring an end" to that investigation.
Republicans on the House Intelligence Committee, which spent the past year conducting a parallel investigation, recently said they had drafted a report concluding no collusion or coordination between Mr Trump's presidential campaign and Russia. Committee Democrats vehemently disagreed.
"The Mueller probe should never have been started in that there was no collusion and there was no crime," Mr Trump tweeted Saturday.
"It was based on fraudulent activities and a Fake Dossier paid for by Crooked Hillary and the DNC (Democratic National Committee), and improperly used in FISA (Foreign Intelligence Surveillance Court) COURT for surveillance of my campaign. WITCH HUNT!"
The Mueller probe should never have been started in that there was no collusion and there was no crime. It was based on fraudulent activities and a Fake Dossier paid for by Crooked Hillary and the DNC, and improperly used in FISA COURT for surveillance of my campaign. WITCH HUNT!— Donald J. Trump (@realDonaldTrump) March 18, 2018
Mr Trump was referring to a dossier of unfavourable research funded by the Democratic Party and Hillary Clinton's campaign.
Likely adding to Mr Trump's growing frustration, The New York Times reported last week that MrMueller had subpoenaed the Trump Organisation and requested Russia-related documents.
Mr Trump had said Mr Mueller would cross a red line with such a step.
"Why does the Mueller team have 13 hardened Democrats, some big Crooked Hillary supporters, and Zero Republicans?" Mr Trump tweeted Sunday.
Why does the Mueller team have 13 hardened Democrats, some big Crooked Hillary supporters, and Zero Republicans? Another Dem recently added...does anyone think this is fair? And yet, there is NO COLLUSION!— Donald J. Trump (@realDonaldTrump) March 18, 2018
Some of Mr Mueller's investigators indeed have contributed to Democratic political candidates, but Justice Department policy and federal service law bar discrimination in the hiring of career positions on the basis of political affiliation. Mr Mueller is a Republican.
The deeply frustrated president has fumed to confidants that the Mueller probe is "going to choke the life out of" his presidency if allowed to continue unabated indefinitely, according to an outside adviser who insisted on anonymity.
Mr Trump has long believed that the entrenched bureaucracy, particularly at the Justice Department and FBI, is out to thwart him.
He also fumed to one confidant after seeing a promotion for Mr Comey's forthcoming book, and believes the former FBI director will seek to enrich himself by besmirching Mr Trump's reputation.
Mr Comey's book, A Higher Loyalty, topped Amazon's best-seller list on Sunday.