President Donald Trump said on Sunday that it will be difficult to get his massive voter fraud and electoral malpractice allegations heard before the US Supreme Court, accusing the courts of refusing to hear his case and reiterating that he will not concede that he lost the election.

In his first TV interview since losing his re-election bid, Trump, who has refused to concede the November 3 presidential election and has had most of his legal challenges dismissed, moaned without evidence that his election lawsuits had been unfairly blocked and questioned the judicial system of the country.

"We're trying to put the evidence in, and the judges won't allow us to do it. We have so much evidence. You probably saw Wednesday last week we had a hearing in Gettysburg, Pennsylvania. … Unbelievable witnesses, highly-respected people, that were truly aggrieved," Trump told Fox News.

This was Trump's first interview after the declaration of election results in which Democratic presidential candidate Joe Biden emerged as the winner. President-elect Biden is now going ahead with the transition plan.

"We're not allowed to put in our proof. They say you don't have standing. I would like to file one nice big beautiful lawsuit, talking about this and many other things, with tremendous proof. We have affidavits, we have hundreds and hundreds of affidavits," Trump asserted.

"You mean as president of the United States, I don't have standing? What kind of a court system is this?" he asked during the interview over the phone that lasted for about 45 minutes.

Observing that the Supreme Court needs to be willing to make a "real big" decision, the president rued that it was hard to get into the apex court.

"The problem is, it's hard to get into the Supreme Court. I've got the best Supreme Court advocates, lawyers that want to argue the case if it gets there," he said. Even as early this week he gave necessary directions to government officials to start the transition process, the president said that he is unlikely to change his mind about election results for the next six months.

"It's not like you're going to change my mind. In other words, my mind will not change in six months. There was tremendous cheating here," Trump said, indicating that he will continue to push for all possible legal remedies to address his allegation of election malpractice.

"I'm going to use 125 per cent of my energy to do it," he said.

Trump refuses to concede the 2020 electio. His is rival Biden is announcing Cabinet members and plans for when he takes office in January.

On Friday, Trump claimed Biden must prove that the votes he received in the election were not “illegally obtained” in order to enter the White House.

Case after case has been rejected by judges around the country. The latest rejection came from the Pennsylvania Supreme Court, which on Saturday turned down a lawsuit filed by Trump supporters seeking to overturn Biden's win in the state.