A US federal judge has ordered a recount of Michigan's presidential ballots.
The judge directed the state start the recount and complete the process by 13 December.
US President-elect Donald Trump at the White House after a meeting with President Barack Obama. Photo: AFP
Lawsuits have also been filed in Pennsylvania and Wisconsin, which bucked their history of supporting Democrats and handed Republican Donald Trump narrow wins in last month's election.
Green Party candidate Jill Stein has pushed for recounts in the three states. Some voting machines in Pennsylvania lacked a paper trail, making them vulnerable to hacking or other problems, she said.
Meanwhile, Mr Trump has named Ben Carson as his secretary of housing and urban development.
Mr Carson is a retired neurosurgeon who ran against Mr Trump in the Republican primary, pulling out of the contest in March.
Outgoing president Barack Obama won Michigan in 2012.
Trump and Gore talk climate change
Mr Trump has also recently met with former vice president Al Gore, an environmental activist who has devoted years to fighting climate change.
Mr Gore said he had a lengthy and productive session with the president-elect.
In the past, Mr Trump has dismissed the idea of man-made climate change as a hoax.
He said during the campaign he would try to get the US out of the Paris Agreement to reduce global emissions of fossil fuels.
However, last month he told the New York Times he had an open mind on this.