WASHINGTON • United States President Donald Trump's Postal Service chief tried to neutralise complaints by suspending his operational changes, but he failed to silence accusations that he is hampering the agency's ability to handle voting by mail.

Postmaster General Louis DeJoy's retreat followed mounting pressure from Democrats, including an Aug 5 exchange with top lawmakers that Senate Minority Leader Chuck Schumer described as "heated". Congress scheduled two hearings with Mr DeJoy in the coming days and the House plans to vote on a postal-funding measure on Saturday.

At heart are concerns that Mr Trump, running behind Democrat Joe Biden in polls, is mounting a politically driven campaign to hobble the Postal Service. The President has repeatedly claimed - without evidence - that widespread mail-in voting leads to fraud.

Mr DeJoy said on Tuesday that he was suspending removals of mail-sorting machines and blue collection boxes in various cities, moves that had been billed as overdue cost-cutting.

He pledged that retail hours would not change, mail-processing facilities would not be shut and equipment would remain where it was.

"Overtime has, and will continue to be, approved as needed."

But it remains unclear if changes already made would be reversed.

"There are unanswered questions that certainly need to be clarified," said former deputy postmaster general Ronald Stroman, who was appointed in 2011 and resigned earlier this year.

"You don't want to reduce your flexibility ahead of a national election where you will have an exponential increase in the amount of absentee ballots," he said on a call with reporters hosted by the Democracy Fund, where he is a senior fellow.

BLOOMBERG