The Pennsylvania Republican Party asked the US Supreme Court Friday to halt the counting of late-arriving ballots in the state, as Democrat Joe Biden took a lead in the tally and was poised to defeat President Donald Trump.

If Biden wins Pennsylvania he wins the presidency.

The last-ditch appeal for an emergency injunction asked the court to freeze the handling of thousands of mailed ballots -- most believed favoring Biden -- that arrived after election day on Tuesday, which Republicans say should be disqualified.

The petition asks the court to order Pennsylvania election officials to sequester all the ballots received after Tuesday and take no action on them.

The petition indicated that the Republican Party could ask the court to revisit a pre-election challenge to the Pennsylvania government's decision to accept late-arriving ballots.

"Given the results of the November 3, 2020 general election, the vote in Pennsylvania may well determine the next president of the United States," they said.

"It is unclear whether all 67 county boards of elections are segregating late-arriving ballots."

Republicans have been fighting for months a state decision to accept mailed-in ballots that are postmarked by November 3 and arrive within three days of election day -- that is, if they arrive by Friday.

The state supreme court ruled the decision legal and it was then appealed in the federal system up to the Supreme Court.

On October 19 the US high court, which had a vacant seat at the time, declined to take the case, splitting 4-4, conservatives vs. liberals

But it also indicated it could take up the case after the vote, and now it has nine members after the Trump-nominated conservative Amy Coney Barrett joined in late October.

The Republican request did not provide any evidence that the ballots are not being segregated already, but said that without a Supreme Court intervention, the Pennsylvania secretary of state could change the guidance given the 67 county boards.  

If the court does issue a stay and accepts the case, it has the potential of ruling invalid the late-arriving ballots, which the state is segregating from others at the moment. 

But it might not make a difference -- the number of late ballots might be significantly fewer than Biden's lead over Trump in the state.