The government of the U.S. state of Pennsylvania, which may hold the key to the outcome of the U.S. presidential election, said Friday that it will finish determining the validity of provisional ballots cast in the election by Tuesday local time.

In America, a provisional ballot is used to record a vote when there are questions about a given voter's eligibility that must be resolved before the vote can count.

In a press release, the Pennsylvania state government said that under state law, the election board must determine the validity of every single provisional ballot within seven days of election day.

The key to this process is identifying duplicate votes.

The New York Times said Friday that 100-thousand provisional ballots and a similar number of mail-in ballots have yet to be counted in Pennsylvania.

According to CNN, Democratic challenger Joe Biden is leading President Trump by about 20-thousand votes in the battleground state as of late Friday U.S. time.