Bowing to mounting pressure, the Trump administration has appointed a former FBI director to lead an investigation into possible ties between the President's election campaign and Russia.
The appointment of Robert Mueller comes amid a growing Democratic outcry for someone outside the US Justice Department to handle the politically charged investigation.
Donald Trump said the investigation will show there was no collusion between his presidential campaign and a foreign power.
"As I have stated many times, a thorough investigation will confirm what we already know - there was no collusion between my campaign and any foreign entity," he said in a statement released by the White House.
"I look forward to this matter concluding quickly. In the meantime, I will never stop fighting for the people and the issues that matter most to the future of our country."
Mr Mueller, whose appointment was announced by the Justice Department, will oversee an inquiry into alleged interference by Moscow in last year's US election and any ties with the Trump campaign.
"I accept this responsibility and will discharge it to the best of my ability," he said in a brief statement.
Sky News US Correspondent Amanda Walker said: "Democrats had been calling for a special prosecutor to be appointed. They wanted someone who wasn't a Trump loyalist, and certainly a former FBI Director such as Robert Mueller will be regarded widely as fitting that bill."
"The fact we are now looking at a special prosecutor, who is widely regarded as an independent figure, to be leading this investigation will calm a lot of fears, particularly felt very strongly among Democrats at the moment".
The New York Times reported this week that Mr Trump asked then-FBI chief James Comey to end an investigation into former national security adviser Michael Flynn.
The newspaper and other reports cited a memo Mr Comey wrote immediately after the 14 February meeting.
On Wednesday, the embattled President said "no politician in history" has been "treated worse or more unfairly" than he has.
He was speaking on the day he faced calls to be impeached over his handling of the Comey scandal and his relationship with Russia.
Speaking to new recruits at a coastguard graduation ceremony in New London, Connecticut, he quickly turned the focus on his recent difficulties.
"Over the course of your life you will find that things are not always fair," he said.
"You will find that things happen to you that you do not deserve, and that are not always warranted, but you have to put your head down and fight, fight, fight!"
Mr Trump added: "Never, ever, ever give up - things will work out just fine.
"Look at the way I've been treated lately - especially by the media.
"No politician in history … has been treated worse or more unfairly.
"You can't let them get you down. You can't let the critics and the naysayers get in the way of your dreams.
"I guess that's why we won.
"Adversity makes you stronger - don't give in, don't back down and never stop doing what you know is right.
"Nothing worth doing ever, ever, ever came easy."
Earlier, Vladimir Putin said he was willing to hand over a transcript of a discussion between Mr Trump and senior Russian officials.
The US President allegedly disclosed highly classified informationabout "terrorism and airline flight safety" while meeting foreign minister Sergei Lavrov and ambassador Sergei Kislyak at the White House last week.
However, Mr Putin said Mr Trump did not pass over secrets and dismissed the scandal as "political schizophrenia".