Republican President-elect Donald Trump has described an impending recount of votes in Wisconsin as a "scam".
Mr Trump, who narrowly won the state, said the results "should be respected instead of being challenged or abused".
Green Party candidate Jill Stein had initiated the recount. She also wants recounts in Michigan and Pennsylvania, citing "statistical anomalies".
Democratic candidate Hillary Clinton's campaign has said it would participate in Wisconsin's recount.
Results would need to be overturned in all three states to alter the outcome of the 8 November presidential election.
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In a statement released by his transition team on Saturday, Mr Trump accused Dr Stein of trying to "fill her coffers with money" on the pretext of asking for donations towards a recount.
"The people have spoken and the election is over," the statement said.
Dr Stein defended her recount initiative, telling CNN that "the point to drive home here is that having a secure elections process benefits us all".
She also suggested that she was open to looking at recounts in other states - not just Wisconsin, Michigan and Pennsylvania.
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Meanwhile, the Clinton campaign's general counsel, Marc Elias, said the camp and outside experts had been "conducting an extensive review of election results, searching for any signs that the voting process had been tampered with".
He said there was no evidence to conclude the election had been sabotaged, but "we have an obligation to the more than 64 million Americans who cast ballots for Hillary Clinton to participate in ongoing proceedings to ensure that an accurate vote count will be reported".
Clinton camp joins in
Mr Elias noted that the number of votes separating Mr Trump and Mrs Clinton in the closest of the three states - Michigan - "well exceeds the largest margin ever overcome in a recount".
However, he said the campaign would join in "on principle" in the Midwestern states if Dr Stein followed through on her promise.
The Green Party nominee reportedly wants to be sure computer hackers did not skew the poll in favour of Mr Trump.
Hillary Clinton has conceded defeat in the presidential elections
Concerns over possible Russian interference had been expressed in the run-up to the vote.
The US government has said Russian state actors were behind hacks on the Democratic National Committee, a claim denied by Moscow.
The Wisconsin Elections Commission said it had received recount petitions, and the process would begin after Dr Stein's campaign had paid the fee, which the commission was still calculating.
Dr Stein's campaign needs to raise millions of dollars to cover the fees for the vote recount in all three states.
Her website says nearly $6m (£4.8m; €5.6m) has already been raised toward a $7m target. It says this is enough to fund the recounts in Wisconsin and Pennsylvania.
The deadline for the petition for the recount in Wisconsin was Friday, while Pennsylvania's deadline is Monday, and Michigan's is Wednesday.
Michigan is yet to declare its final results.
Wisconsin provides only 10 votes in the crucial electoral college that gave Mr Trump victory in the 8 November election.
Wins there for Mrs Clinton, as well as in Michigan (16 electoral votes) and Pennsylvania (20 electoral votes), would have clinched the presidency for the Democrat.
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