Donald Trump repeats unfounded claims of US election corruption as he rallies for Republican Senate candidates in Georgia

Donald Trump has told crowds in Georgia, without evidence, he has "never lost an election" and that he'd be a "very gracious loser", in his first political rally since losing the presidential election.

Key points: Donald Trump has refused to acknowledge the results of the 2020 election

Donald Trump has refused to acknowledge the results of the 2020 election In Georgia, Mr Biden won by about 12,500 votes

In Georgia, Mr Biden won by about 12,500 votes Mr Trump tried to convince Georgian authorities to conduct another audit

Amid chants of "stop the steal", "four more years" and "we love you" from maskless supporters in the town of Valdosta, Mr Trump began his speech repeating falsehoods about voter fraud.

"You know we won Georgia, just so you understand," Mr Trump told rallygoers.

"Let them steal Georgia again, you'll never be able to look yourself in the mirror."

Mr Trump has refused to concede his defeat to president-elect Joe Biden, and has instead repeatedly and without evidence asserted widespread fraud.

But his claims have been rejected by state and federal officials across the country, and his campaign's numerous legal challenges have almost all failed.

Mr Trump said at the rally his challenge to the election result was headed to the US Supreme Court "very shortly," without elaborating.

Legal experts do not see a path to the nation's highest court, however.

There are no known reports of US mail ballots found in ceilings or leather bags. ( AP: Rich Pedroncelli )

"When you look at all of the corruption and all of the problems having to do with this election, all I can do is campaign and wait for the numbers," he said.

"But when the numbers come out of ceilings and come out of a leather bag, you start to say, 'what's going on?'"

In Georgia, Mr Biden won by about 12,500 votes out of 5 million cast, with a subsequent vote audit by the state's Republican leaders also confirming Mr Biden's win.

But this was denied by Mr Trump.

"You know we won Georgia, just so you understand," Mr Trump said.

"I'm not watching to see if people walk into polling places with black briefcases with a ribbon around them. That's up to [Georgia's] Government."

Later in the speech, Mr Trump again accused the Democrats of "stealing" the election, and and warned crowds of the risks of a purported "radical left agenda that hates America" if Georgians didn't vote for Republican Senate candidates.

"These people [Democrats] are sick — they'll do anything to beat you," Mr Trump said.

"If I lost, I'd be a very gracious loser … [but] you can't accept when they steal and rape and rob.

"The Democrats have tried to steal."

Trump in Georgia to aid Republicans' Senate campaign

Mr Trump said he travelled to Georgia to help "ensure" two Republicans — David Perdue and Kelly Loeffler — win what are probably the most important Senate runoff elections in US history.

The results will determine which party controls the Senate, as results are still neck and neck.

Senate elections in Georgia will decide whether Mr Biden's presidency will be unimpeded or not. ( AP: Ben Gray )

Mr Trump said voters could and should refuse to accept what he called the "rigged" presidential election results while also casting ballots for Mr Perdue and Ms Loeffler in the runoffs.

"If you don't vote, the socialists and the communists win," he said.

"We can fight for the presidency and fight to elect our two great senators, and we can do it at the same time."

At another point in the rally, Mr Trump teed up a video for the crowd attacking the senators' Democratic opponents as extreme leftists.

Prior to the rally, Mr Trump has also attacked Republicans who refused to back him, including Georgia's Governor, Brian Kemp, and its Secretary of State, Brad Raffensperger.

On Saturday, Mr Trump phoned Mr Kemp and pressured him on Twitter to take further steps to reconsider Georgia's result.

"I will easily and quickly win Georgia if Governor @BrianKempGA or the Secretary of State permit a simple signature verification … Why are these two 'Republicans' saying no?" Mr Trump wrote on Twitter.

After Mr Kemp responded on Twitter that he had "publicly called for a signature audit three times", Mr Trump said that wasn't good enough, and added in a second tweet that the Governor should immediately call a special session of the state legislature.

"Your people are refusing to do what you ask. What are they hiding?" Mr Trump said.

Mr Biden won the election with 306 electoral college votes — against the 270 required — to Trump's 232.

The electoral college will meet on December 14 to formalise the outcome.