Republicans warn Trump over Mueller's Russia inquiry

Key Republicans have warned President Donald Trump not to interfere with special counsel Robert Mueller and his team's on going probe into alleged Russian interference in the 2016 presidential election, the media reported.

The warnings came after Trump on Sunday morning criticised Mueller on Twitter, one day after his lawyer John Dowd issued a statement saying he prays for the Justice Department to end the special counsel's investigation.

He added that it was dominated by "hardened Democrats".

Arizona Republican Senator Jeff Flake on Sunday told CNN that he expected his colleagues in Congress to push back on the President's comments on Mueller and any potential move to force the end of the probe.

"I mean, talking to my colleagues all along it was, you know, once he goes after Mueller, then we'll take action," Flake said.

He called Attorney General Jeff Sessions' firing of former FBI Deputy Director Andrew McCabe late Friday, who was ousted a little over 24 hours before he was to retire, as a "horrible day for democracy".

South Carolina Republican Senator Lindsey Graham said that he continues to believe that any attempt to fire Mueller would be catastrophic for Trump.

"If he tried to do that, that would be the beginning of the end of his presidency," Graham told CNN.

Graham also said the Senate Judiciary Committee should conduct a public hearing on the firing of McCabe for the sake of transparency.

Florida Republican Senator Marco Rubio told NBC News: "I remain confident that the special counsel is going to conduct a probe that is fair and thorough and is going to arrive at the truth..."

Meanwhile, Democrat leaders also voiced their disapproval of Trump's tweet.

Senate Minority Leader Chuck Schumer and California Democratic Representative Adam Schiff both called on their Republican colleagues to temper the President.

Also on Sunday, White House lawyer Ty Cobb said in a statement: "In response to media speculation... The White House yet again confirms that the President is not considering or discussing the firing of the Special Counsel," the BBC reported.