The US Postal Service failed to meet the deadline for a sweep that was ordered for 300,000 mail-in ballots that were unaccounted for.
Emmet Sullivan, a federal judge in the District of Columbia, had decreed that the operation should begin before 3pm to “ensure that no ballots have been held up and that any identified ballots are immediately sent out for delivery”.
Mr Sullivan asked for an update on the undelivered ballots in 12 districts, including Florida, Detroit, Central Pennsylvania and Alabama, by 4.30pm but the US Postal Service did not meet it.
The order was issued after the Postal Service gave data to the court that showed about 300,000 ballots had not been scanned to confirm delivery, yet the service said they had been processed.
Those who searched the plants and processing ballots for the postal service were in a race against time because some states do not count ballots delivered after a certain time on election day.
Record numbers of US voters have chosen to mail in their ballots this year to avoid queues at polling stations during the pandemic.
Before election day, more than 100 million people cast early ballots either by mail or in person, said the US Elections Project at the University of Florida.
Some postal districts were reporting slow delivery times for days leading up to election day.That prompted Mr Sullivan to express concern over Central Pennsylvania, Detroit and Philadelphia, which were processing only 69, 78 and 79 per cent of ballots on time on Monday.
His last-minute ruling came after voting rights organisation Vote Forward filed a lawsuit to ensure all mail-in votes are counted.
"No one should be disenfranchised for something that is out of their control," Shankar Duraiswamy, a lawyer for Vote Forward, told the Los Angeles Times.
“It’s important that the Postal Service does everything in its power to make sure that doesn’t happen.
The Postal Service’s ability to handle the surge of mail-in ballots became a concern after Postmaster General Louis DeJoy, a Republican donor, introduced policy changes that delayed mail nationwide this summer.