Trump promises peace, but turmoil over Russia probe and media intensifies

US President Donald Trump speaks during a post-election press conference in the East Room of the White House in Washington, DC. (MANDEL NGAN/AFP)

Nothing provokes the anger of the fiery and unconventional president more than special counsel Robert Mueller's investigation into whether his campaign colluded with Russian agents during his 2016 election.

Trump has continuously threatened that he has the power to shut down what he calls "a witch hunt" and on Wednesday he took the first potential step when he replaced his attorney general, Jeff Sessions, with loyalist Matthew Whitaker.

The switch, announced on Trump's Twitter feed, provoked consternation across Washington, where politicians from both sides of the aisle have long warned that political interference in Mueller's work cannot be tolerated.

Democrats, who won the lower house of Congress in Tuesday's midterm elections, now see Trump as close to crossing that line with the ultimate goal of covering up alleged crimes.

"The rule of law is disappearing before our eyes," tweeted Sally Yates, a deputy attorney general under Trump's predecessor Barack Obama and briefly in the top job under Trump before he sacked her.

"He wants a political crony to protect him from the investigation of his own campaign," she said.

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The midterm elections saw the Democrats win control of the lower house of Congress for the first time in eight years, meaning that from January onwards Trump will finally face an opposition that has teeth.

However, with Republicans tightening their grip on the Senate, an initially magnanimous-sounding Trump suggested that a divided Congress would bring opportunity for bipartisan cooperation - something in low supply in Washington.

"Everybody is in love," he said at a White House press conference.

Only minutes later, a series of questions he found overly hostile sent him into a most un-loving blowup.

CNN's Jim Acosta, who regularly spars with Trump and his spokeswoman Sarah Sanders, annoyed the president by asking if he'd demonised immigrants during the midterms election campaign and then went on to ask about the Russia probe.

An ever-more exasperated Trump ordered him to give up the mic and Acosta refused, with Trump branding him an "enemy of the people" and a "rude, terrible person."

The row, carried live on national TV networks, was followed by Trump issuing angry put-downs to several other reporters. Shortly after, the White House took the extremely rare measure of revoking Acosta's press pass.

On Thursday, the Acosta incident entered even more bizarre territory when the White House was accused of tweeting a video doctored to make the reporter appear more aggressive in fending off the female press aide who tried to remove his mic.

Answering allegations that the White House had used a clip edited by a notorious right-wing conspiracy theorist, Trump spokeswoman Sarah Sanders said: "We stand by our statement."

"The question is: did the reporter make contact or not? The video is clear, he did," she said.

'CONSTITUTIONAL CRISIS'

Spats between Trump and journalists can sometimes seem circus-like, but critics say the president's hot temper illustrates his deeper disdain for Washington norms - and allegedly for the law.

Those concerns are now focused on the future of the Mueller probe, which began as a look into alleged links with Russians seeking to disrupt the election and expanded into an investigation of billionaire Trump's murky finances, including his business ties to Russia.

As Mueller has got closer to the heart of the Trump family's closely guarded financial secrets, the president has become more enraged.

"It was supposed to be on collusion. There's no collusion," Trump said on Wednesday. "They went after people with tax problems, from years ago. They went after people with loans and other things. Had nothing to do with my campaign."

Whitaker now becomes Mueller's new boss and judging by past statements he will be sympathetic towards Trump.

Sessions had recused himself from the investigation, because of his own contacts with Russians during the 2016 campaign, instead handing responsibility for Mueller to his deputy Rod Rosenstein. An infuriated Trump responded by repeatedly and publicly seeking to humiliate Sessions.

Whitaker has made no public comment since being named, but he has previously shown distinct skepticism about the probe, including calling for its scope to be curtailed.

In 2017 he even used Trump's words, warning against Mueller engaging in a "witch hunt."

In the House of Representatives, the senior Democrat on the Intelligence Committee - which Democrats will control from January - sounded the alarm.

"Interference with the special counsel's investigation would cause a constitutional crisis and undermine the rule of law," Adam Schiff said.

"If the president seeks to interfere in the impartial administration of justice, the Congress must stop him. No one is above the law," Schiff said.

Republicans, however, have been mostly silent.

One of the exceptions, Senator Susan Collins, said non-interference in the Mueller probe was "imperative."