Washington DC - President Donald Trump on Monday pardoned Rod Blagojevich, the former Illinois governor whose prison sentence for corruption he commuted five years ago during his first term.

Democrat Blagojevich was removed from his governor's post in 2009 and later convicted of essentially selling the Senate seat vacated by Barack Obama when he won the US presidency in 2008.

"It was sort of a terrible injustice. They just went after him, they go after a lot of people. These are bad people on the other side," Trump told reporters as he signed the pardon in the Oval Office.

"I think he's a very fine person, and this shouldn't have happened."

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Asked whether he was considering Blagojevich to be US ambassador to Serbia, as had been reported, Trump said: "No, but I would. He's now cleaner than anybody in this room."

Back in 2020, Trump was vague about his reasoning for freeing Blagojevich, who was sentenced to 14 years.

The president noted that he'd once performed with Blagojevich during his reality show The Apprentice and said he "seemed like a very nice person," but added: "I don't know him very well."

"He served eight years in jail. He has a long time to go. Many people disagree with the sentence," Trump told reporters.

Trump has freely exercised the US president's wide-ranging powers to issue pardons since he returned to the White House on January 20.

On the evening of his inauguration, he pardoned some 1,500 people involved in the violent January 6, 2021 US Capitol riot.

He has also pardoned two dozen anti-abortion protesters who attacked a clinic in 2020, as well as Ross Ulbricht, the man behind the Silk Road online marketplace that facilitated millions of dollars of drug sales.