DAVID PERDUE AND Jon Ossoff will face each other in a run-off for a Senate seat, one of two high-profile contests in Georgia that could determine which party controls the upper chamber.

Libertarian candidate Shane Hazel was able to get enough votes so that neither Mr Perdue nor Mr Ossoff was able to clear the 50 per cent threshold needed for an outright win.

Thousands of absentee ballots and in-person votes cast early needed to be counted after Election Night passed, forcing a long and tense wait before the race could be called.

The contest will be one of two in Georgia in January that is likely to settle which party controls the Senate.

Democrat Raphael Warnock and Senator Kelly Loeffler, the Republican-appointed last year, will also compete in a run-off on the same day.

Nationally, the Senate stands at 48-48.

But Republicans lead uncalled races in Alaska and North Carolina, so the ultimate balance is likely to come down to what happens in the Georgia run-offs.

Both sides promised unlimited funds would flow to the campaigns and onto the airwaves, and they predicted an all-star cast of campaigners for a state that in recent weeks drew visits from Democratic presidential nominee Joe Biden, President Donald Trump, Vice President Mike Pence, Democratic vice presidential nominee Kamala Harris and former President Barack Obama.

The race between Mr Ossoff and Mr Perdue, a close ally of Mr Trump, has been characterised by sharp attack adverts but relatively moderate political positions.

Both candidates pivoted to the middle vying for a state Mr Trump won handily four years ago, but where swaths of suburbia have shown signs of disillusionment with the president.

Mr Perdue sought to cast his opponent as backing a “radical socialist agenda,” while Mr Ossoff portrayed Mr Perdue as a “corrupt” Washington insider who has been part of a botched pandemic response.