Billionaire Elon Musk has doubled down on his threat to fire US federal government employees who do not respond to his email asking ‘What did you do last week?’

The US agency that oversees federal workers said they could ignore the weekend email that required the nation’s 2.3 million civil servants to justify their jobs.

Musk, who has been given authority to slash federal spending, had directed workers to provide a five-point summary of their work by midnight on Sunday.

His demand sparked unusual pushback from some agencies.

According to an internal US Justice Department email seen by Reuters, the US Office of Personnel Management told human resources officials at federal agencies on Monday that employees would not be let go for not replying to Musk’s email — nor were staff required to respond to it.

The memo said responding to the email was voluntary. It also urged employees not to share confidential, sensitive or classified information in their responses, a concern of critics of Musk’s action.

But just hours after the backlash, Musk repeated his threats in a post on X.

“Subject to the discretion of the President, they will be given another chance,” he wrote.

“Failure to respond a second time will result in termination.”

The email has raised questions about how much authority the world’s richest person can wield in President Donald Trump’s effort to downsize the US government.

Some agencies nudged their employees to respond.

A senior manager at the General Services Administration, which manages federal buildings, told employees the agency was still encouraging workers to answer the email even if it was voluntary, according to a GSA source.

Similarly, the acting director of OPM emailed agency staff to say that responding with bullet points was voluntary “but strongly encouraged”.

The White House and OPM did not respond to requests for comment.

The countermanding of Musk’s order by some agency leaders was the first sign of internal resistance to his blunt-force approach to downsizing the federal government.

The Department of Health and Human Services advised employees that if they chose to reply, they should keep their responses general and should refrain from identifying specific drugs or contracts they are working on, according to an email reviewed by Reuters.

“Assume that what you write will be read by malign foreign actors and tailor your response accordingly,” the email said.

Musk’s downsizing initiative has rippled into the wider US economy as well, forcing companies that do business with the government to lay off their own workers and defer payments to vendors.

The billionaire’s Saturday message took some administration officials by surprise, according to two sources familiar with the situation.

Adding to the confusion, Trump stood by Musk.

“I thought it was great,” he said at the White House on Monday.

“There was a lot of genius in sending it. We’re trying to find out if people were working.”

In other action, a federal judge blocked the government downsizing team created by Trump and led by Musk from accessing sensitive data maintained by the US Education Department and the OPM.

Also, a group of labour unions that have asked a federal judge to stop the mass firings updated their lawsuit to request that Musk’s email be ruled illegal.

Prior to the OPM directive, senior officials at Justice, as well as the departments of Defence, State and Homeland Security and several other agencies had told workers not to respond outside their established chain of command.

The Transportation Department, the Treasury Department and independent agencies like the Federal Trade Commission and the Federal Communications Commission have told employees to answer Musk’s message.

Musk has revelled in the upheaval, even wielding a chainsaw at a conservative political conference last week.

More than 20,000 workers have been laid off as part of the downsizing effort.

The confusion echoed the broader turmoil surrounding Trump’s return to power.

Since taking office on January 20, Trump has frozen billions of dollars in foreign assistance and effectively dismantled the US Agency for International Development, stranding medicine and food in warehouses.

-with AAP