America's midterm elections opened Friday in a fog of confusion over mail voting, with ballots already going out as US President Donald Trump presses courts to let him impose sweeping new restrictions on how they are handled. North Carolina became the first state authorised to begin circulating ballots, formally launching an election season that culminates on November 3 and will determine control of Congress for the final two years of Trump's term. Yet voters and election officials still do not know what rules may govern millions of mail ballots, as Trump asks the Supreme Court to revive curbs blocked by a federal judge and as states scramble to prepare for changes that could come after voting has begun. The dispute has been compounded by whistleblower allegations that a new postal service verification system was rushed, inadequately tested and could delay or even disqualify entire batches of ballots because of a single barcode problem. Read moreUS Postal Service whistleblower warns new system could disrupt midterm election voting A federal judge weighing whether to extend the temporary block on Trump's plan warned Thursday that hurried changes could cause widespread disruption. "We're not playing an intellectual puzzle game," Judge Indira Talwani reportedly told a lawyer defending the restrictions, in remarks widely picked up by US media. "We're talking about people's right to vote." Trump's March executive order would require states to provide the United States Postal Service (USPS) with lists of eligible mail voters through a new federal portal.