It comes as the trial of former Trump campaign manager Paul Manafort continues in the US
Donald Trump has called on US Attorney General Jeff Sessions to end the special counsel probe into alleged Russian interference in the 2016 election "right now".
The US president has frequently slammed the investigation, which is being led by Robert Mueller, as a 'witch hunt'.
However, the latest intervention marks a significant escalation of his rhetoric against the probe.
President Trump claimed action is needed as the probe is 'staining our country'.
..This is a terrible situation and Attorney General Jeff Sessions should stop this Rigged Witch Hunt right now, before it continues to stain our country any further. Bob Mueller is totally conflicted, and his 17 Angry Democrats that are doing his dirty work are a disgrace to USA!— Donald J. Trump (@realDonaldTrump) August 1, 2018
According to the New York Times, President Trump's lawyers moved to clarify the tweet - saying it was merely an opinion and not an order to a cabinet member.
Jeff Sessions last year recused himself from any involvement in the special counsel probe, following reports of his contacts with the Russian ambassador in 2016.
Chuck Schumer, the Democratic minority leader in the Senate, said the US president's latest statement was "just another attempt to make the American people look at his latest shiny object".
He noted: "The Mueller-Rosenstein investigation is making progress at record speed: 35 indictments, 5 guilty pleas & Trump’s campaign chairman on trial."
In a series of tweets today, President Trump also spoke about Paul Manafort - the former Trump campaign manager whose trial began in the US yesterday.
69-year-old Manafort faces charges relating to money he is accused of funnelling through offshore accounts.
The charges emerged during the ongoing Mueller investigation, although largely predate Mr Manafort's work with the Trump campaign.
Today, President Trump wrote: "Paul Manafort worked for Ronald Reagan, Bob Dole and many other highly prominent and respected political leaders. He worked for me for a very short time.
"Why didn’t government tell me that he was under investigation. These old charges have nothing to do with Collusion - a Hoax!"
Looking back on history, who was treated worse, Alfonse Capone, legendary mob boss, killer and “Public Enemy Number One,” or Paul Manafort, political operative & Reagan/Dole darling, now serving solitary confinement - although convicted of nothing? Where is the Russian Collusion?— Donald J. Trump (@realDonaldTrump) August 1, 2018
The trial is continuing today at a court in Virginia.