Have absolute right to pardon myself: Trump

US President Donald Trump said today that he has "absolute right to pardon" himself as he slammed the opposition Democratic party for witch-hunt against him alleging that the appointment of a special counsel is unconstitutional.

Former FBI Director Robert Mueller is the Special Counsel appointed by the Department of Justice to investigate into the allegation of Russian interference in the 2016 presidential elections in Trump's favour.

"The appointment of the Special Counsel is totally UNCONSTITUTIONAL! Despite that, we play the game because I, unlike the Democrats, have done nothing wrong!" Trump tweeted.

"As has been stated by numerous legal scholars, I have the absolute right to PARDON myself, but why would I do that when I have done nothing wrong?" he tweeted.

"In the meantime, the never ending Witch Hunt, led by 13 very Angry and Conflicted Democrats (& others) continues into the mid-terms!" he said, unleashing a series of tweets on completing 500 days in office.

Trump claimed that he has accomplished more than any other presidents in the first 500 days in office.

"This is my 500th. Day in Office and we have accomplished a lot - many believe more than any President in his first 500 days," he said.

"Massive Tax & Regulation Cuts, Military & Vets, Lower Crime & Illegal Immigration, Stronger Borders, Judgeships, Best Economy & Jobs EVER, and much more...," he said.

"We had Repeal & Replace done (and the saving to our country of one trillion dollars) except for one person, but it is getting done anyway. Individual Mandate is gone and great, less expensive plans will be announced this month. Drug prices coming down & Right to Try! tweeted the US president.