Georgia election officials have announced an audit of presidential election results that will trigger a full hand recount.

Georgia Secretary of State Brad Raffensperger said at a news conference that his office wants the process to begin by the end of the week and he expects it to take until November 20.

President-elect Joe Biden leads President Donald Trump by about 14,000 votes out of nearly 5 million votes counted in the state.

Nearly all ballots have been counted, though counties have until Friday (local time) to certify their results.

There is no mandatory recount law in Georgia, but state law provides that option to a trailing candidate if the margin is less than 0.5 percentage points.

Mr Biden's lead stood at 0.28 percentage points as of Wednesday morning (local time).

How a recount in Georgia will work

For the hand recount, election officers will work with the paper ballots in batches, dividing them into piles for each candidate.

Then they will run the piles through machines to count the number of ballots for each candidate, the scanners will not read the data on the ballots.

After results from the hand recount are certified, the losing campaign can then request another recount, which will be performed by machine.

"Mathematically, you actually have to do a full hand-by-hand recount of all because the margin is so close," Mr Raffensperger said.

"We want to start this before the week is up."

Following Mr Biden's victory, Mr Trump has sought to discredit the integrity of the election and argued without evidence that the results will be overturned.

There have been at least 31 statewide recounts since 2000. Of those, only three changed the outcome of the election.

The initial margins in those races were all under 300 votes.

US Senate control to be decided by January runoffs in Georgia

As news of a recount in Georgia filtered through it was also confirmed the state will play a pivotal role in determining which party has the balance of power in the US Senate.

In Alaska Republican Senator Dan Sullivan won re-election leaving control of the Senate to be determined in January by two runoff elections in Georgia.

Coming a day after Republican Senator Thom Tillis won re-election in North Carolina, Mr Sullivan's victory confirms that Democratic hopes of winning a majority of seats, and with it the power to support Mr Biden's agenda, will come down to the two Georgia elections scheduled for January 5.

With Mr Biden's White House victory, Democrats need to pick up three Republican Senate seats to hold 50 seats, with Vice-President-elect Kamala Harris wielding the tie-breaking vote.

Democrats won Republican seats in Arizona and Colorado in last week's election. But they lost a seat in Alabama, reducing their net gain to a single seat.

In Georgia, Republican Senators David Perdue and Kelly Loeffler face challenges from Democrats Jon Ossoff and Raphael Warnock, respectively.

AP/Reuters