Supporters of president-elect Donald Trump have moved to maintain his narrow victories in three states, pursuing legal challenges aimed at halting the Green Party's requests for long-shot recounts of the presidential votes there.
Lawsuits were pending in Michigan, Pennsylvania and Wisconsin, three "Rust Belt" states which bucked their history of supporting Democrats and gave Trump, a Republican, thin wins in the November 8 election.
The Green Party has said its requests for recounts in those states are focused on ensuring the integrity of the US voting system and not on changing the result of the election.
Even if the recounts take place, they are extremely unlikely to change the overall outcome of the election, in which Trump beat Democrat Hillary Clinton.
Green Party candidate Jill Stein, who garnered only about 1 per cent of the vote, has said the recount campaign is not targeted at Trump or Clinton.
Michigan Attorney General Bill Schuette, a Republican, said on Friday he had filed a lawsuit to halt the requested recount in his state.
Recounting all of the state's votes "threatens to silence all Michigan votes for president" because of an impending federal deadline to finalise the state's results, Schuette said in a statement.
The presidential 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. Federal law requires states to resolve disputes over the appointment of electors by December 13.
Trump far surpassed the 270 electoral votes needed to win, with 306 electoral votes, and the recount would have to flip the result to Clinton in all three states to change the overall result.
In the popular vote, Clinton won 2.5 million more votes than Trump, according to the Cook Political Report.
Schuette also criticised Stein for the potential expense of a recount, although she said last week that she had raised $US3.5 million ($A4.7 million) to cover some costs.
A Schuette spokeswoman said on Friday that Stein had contributed $US787,500 but that it would cost about $US5 million.
The Trump campaign's own lawyers have moved to block recount efforts in Pennsylvania and Michigan, according to court papers in those states. A Pennsylvania court has scheduled a hearing for Monday morning in Harrisburg, the state capital.
In Wisconsin, where the recount is already under way, the Trump-supporting political action committee Great America PAC sued in federal court on Thursday seeking to block a recount there.
The lawsuit cited as legal precedent the US Supreme Court's Bush v Gore decision that ended the 2000 election and Florida recount.
The Wisconsin Republican Party has also filed a complaint over the recount effort in that state, it said.
Stein's campaign manager, David Cobb, criticised the Trump effort in Pennsylvania in particular, saying in a statement: "We will continue to help Pennsylvania voters make sure that the election in Pennsylvania had integrity and that their votes counted."
Stein's website said on Friday the Green Party had raised $US6.8 million so far for the recount and had a goal of $US9.5 million.
Lawyers for Clinton have said they would take part in the Wisconsin recount effort to ensure her campaign is legally represented, and that they would do the same if necessary in Michigan and Pennsylvania.
