US President-elect Joe Biden and President Donald Trump will campaign next week in Georgia, holding duelling events on the eve of runoff elections that will determine who controls the US Senate and the fate of Mr Biden’s legislative agenda.

The visits come as Mr Trump escalates his fight with fellow Republican leaders in the state for not supporting his bid to overturn the election results. On Wednesday (local time), he called for the state’s Republican governor, Brian Kemp, to resign.

Mr Biden, who takes office on January 20, will travel to Atlanta on Monday to campaign on behalf of Democratic Senate candidates Jon Ossoff and Raphael Warnock, his transition team said on Wednesday. Vice President-elect Kamala Harris will go to Savannah, Georgia, a day earlier.

On the same day Mr Biden appears in Atlanta, Trump will travel to Dalton, Georgia, to hold a “victory rally” to support Republican incumbent Senators Kelly Loeffler and David Perdue.

The candidates square off in an election on Tuesday.

If the Democrats win both seats, the Senate would be split 50-50 with the Republican Party, giving the tie-breaking vote to Ms Harris and control of both congressional chambers to the Democratic Party.

More than 2.5 million votes have already been cast in the runoff races, according to the Georgia secretary of state’s office.

If the Republicans win one or both of the Georgia seats, they will retain a slim majority in the Senate, giving them an opportunity to block Mr Biden’s legislative goals and judicial nominees.

Mr Biden gave a speech in Georgia last month urging voters there to oust Republican Senator Mitch McConnell as majority leader by electing the two Democratic candidates.

Mr McConnell has declined to bring up a bill approved by the Democratic-controlled House of Representatives to increase COVID-19 relief checks to $US2000 from $US600 ($A2600 to $A800).

In doing so, he has been at odds with Mr Trump, who has said a refusal to increase the aid would be a “death wish” for the Republican Party.

Both Mr Loeffler and Mr Perdue have called for increasing the stimulus payments, while Democrats see their support for the measure helping them in Georgia.

Mr Kemp dismissed Trump’s call for his resignation on Wednesday, saying the demands and stream of complaints were a distraction from more pressing issues.

Mr Trump called for Mr Kemp’s resignation in a tweet Wednesday morning in which he called the governor an “obstructionist”.

Mr Trump, who has claimed without evidence that Democrats stole the election through fraud, has repeatedly attacked Mr Kemp for refusing to acknowledge him as the rightful victor in Georgia. Mr Biden won the state by roughly 12,000 votes.

Mr Kemp said the election process should be allowed to play out, noting that the US Congress was set to meet to validate the results on January 6.

“That horse has left the barn in Georgia and it’s headed to DC right now,” Mr Kemp said.

-AAP