America's midterm elections have opened 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 sending out ballots on Friday, 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.

A federal judge on Friday extended her previous temporary block on Trump's plan, a day after warning 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."

The Trump administration is expected to appeal to the Supreme Court against Talwani's new order, which extends her previous block.

Trump's March executive order would require states to provide the US Postal Service with lists of eligible mail voters through a new federal portal.

Ballot envelopes would also need individual barcodes and other design features, with the service empowered to refuse mailings that fail to meet its requirements.

Trump has repeatedly denounced mail voting as corrupt while using it himself – including to vote in Florida's Republican primary just last month.

The uncertainty comes on top of a voting system that already differs dramatically from state to state.

Some automatically send ballots to registered voters, others require voters to request them, while identification requirements, return deadlines and rules for counting late-arriving ballots vary across the country.

Friday marks 60 days before Election Day – the deadline Trump's order itself envisioned for states to submit voter information –while another 18 states are expected to begin distributing ballots roughly 45 days before November 3.

A new Cornell University forecast gives Democrats an eight-in-10 chance of taking the chamber, projecting a roughly 226-209 majority. (AFP)





Edited by Azam Khan