According to an internal document described to Reuters reveals that if adopted as official policy, that could threaten back pay for up to 700,000 furloughed scientists, administrators and other civil servants who have been ordered not to work since the shutdown began on October 1.
That would counteract guidance by Trump's own personnel office, which says a 2019 law signed by Trump guarantees back pay to all employees as soon as possible after a shutdown ends, whether they were furloughed or required to stay on the job.
It also threatens to upend past practise in Washington over the 15 government shutdowns since 1981, when Congress has voted to restore back pay to all employees.
In a draft memo dated Friday, the top lawyer at the White House Office of Management and Budget argued that the 2019 law does not make those payments automatic, but still requires them to be approved by Congress, according to a White House official who spoke on condition of anonymity.
Speaking to reporters at the White House on the seventh day of the shutdown, Trump suggested that not all of those idled should be paid when normal operations resume.
"It depends on who we're talking about," he said without explaining further.
"We're going to take care of our people," he added.
"There are some people that really don't deserve to be taken care of, and we'll take care of them in a different way."
Trump has repeatedly threatened to use the shutdown to lay off thousands of federal workers, on top of the 300,000 he will have pushed out by the end of the year, and his administration has frozen more than $US30 billion ($A45 billion) in transit and green-energy funding for Democratic-leaning cities and states.
During the shutdown, federal agencies are requiring military troops, border guards, air traffic controllers and other "essential" workers to report for duty, even though they are not getting paid.
They could face financial strain as soon as next week, when many would miss their first pay cheque.
The shutdown began October 1 when Congress allowed government funding to expire, and lawmakers have repeatedly rejected duelling Republican and Democratic plans to restore funding.
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