Trump requested the recount in Milwaukee and Dane counties, both heavily liberal, in hopes of undoing Democrat Joe Biden's victory by about 20,600 votes.

With no precedent for a recount reversing such a large margin, Trump's strategy is widely seen as aimed at an eventual court challenge, part of a push in key states to undo his election loss.

A steady stream of Republican complaints in Milwaukee was putting the recount far behind schedule, county clerk George Christenson said.

He said many Trump observers were breaking rules by constantly interrupting vote counters with questions and comments.

"That's unacceptable. (Some of the Trump observers) clearly don't know what they are doing," he said.

At least one Trump observer was escorted out by sheriff's deputies on Saturday after pushing an election official who had lifted her coat from an observer chair.

Another Trump observer was removed on Friday for not wearing a face mask properly as required.

Trump paid $US3 million ($A4.1 million), as required by state law, for the partial recount that began Friday and must conclude by December 1.

His team is seeking to disqualify ballots where election clerks filled in missing address information on the certification envelope where the ballot is inserted, even though the practice has long been accepted in Wisconsin.

The campaign also alleges thousands of absentee ballots don't have proper written paperwork, and that some absentee voters improperly declared themselves "indefinitely confined," a status that allows them to receive a ballot without photo ID.

Those challenges were being rejected.

There have been at least 31 recounts in statewide elections in the US since the most famous one in Florida's presidential election in 2000.

The recounts changed the outcome of three races. All three were decided by hundreds of votes, not thousands.

Australian Associated Press