Green Party candidate Jill Stein has abruptly dropped her petition for a recount of all votes cast in the US presidential election in Pennsylvania after a judge ordered her campaign to post a $US1 million ($1.34 million) bond, according to court documents.

But her team vowed to continue the fight in federal court.

"The Stein campaign will continue to fight for a statewide recount in Pennsylvania," Jonathan Abady, lead counsel to Ms Stein's recount efforts, said in a statement late on Saturday (local time).

Saying it has become clear that "the state court system is so ill-equipped to address this problem", the statement said "we must seek federal court intervention".

The Stein campaign said it would file for emergency relief in the Pennsylvania effort in federal court on Monday, "demanding a statewide recount on constitutional grounds".

The bond was set by the Commonwealth Court of Pennsylvania a day after representatives of President-elect Donald Trump requested a $US10 million bond, according to court papers.

The court gave the petitioners until 5:00pm on Monday to post the bond, but said it could modify the amount if shown good cause. Instead, Ms Stein's campaign withdrew.

"Petitioners are regular citizens of ordinary means. They cannot afford to post the $1 million bond required by the court," wrote attorney Lawrence Otter, informing the court of the decision to withdraw.

Ms Stein, who garnered about 1 per cent of the presidential vote, has also sought recounts in Michigan and Wisconsin, after crowdfunding $US3.5 million for the filing fees.

Mr Trump won narrow victories over Democrat Hillary Clinton in all three battleground states, part of the industrial heartland of the country until manufacturers started leaving for Mexico and other low-wage countries.

Mr Trump and his allies have attempted to stop the initiatives in the states, calling the recount effort a "scam". Mrs Clinton's campaign has said it would take part in the recounts.

"The judge's outrageous demand that voters pay such an exorbitant figure is a shameful, unacceptable barrier to democratic participation," Ms Stein said in a statement.

"No voter in America should be forced to pay thousands of dollars to know if her or his vote was counted."

Even if all the recounts were to take place, the overall election outcome would not likely change.

The race is decided by the electoral college, or a tally of wins from the state-by-state contests, rather than by the popular national vote.

Mr Trump surpassed the 270 electoral votes needed to win, with 306. Recounts would have to flip the result to Mrs Clinton in all three states to change the result.

In the popular vote, Mrs Clinton had more than 2.5 million votes over Mr Trump, the independent Cook Political Report said.

Reuters