US defence department workers could face lie detector tests as the Pentagon investigates alleged leaks of national security information.

The department’s intelligence and law enforcement arms are carrying out the inquiry, which is the latest by Donald Trump‘s administration.

In a memo sent late on Friday, defence secretary Pete Hegseth’s chief of staff called for an investigation into “unauthorised disclosures of national security information” that could include polygraph tests.

Details of the alleged leaks were not included in the memo.

Earlier in the day, Mr Trump was forced to reject reports that Elon Musk would be briefed on US military plans for fighting a hypothetical war with China.

Mr Musk, who is head of the Department of Government Efficiency (DOGE) advisory group, visited the Pentagon on Friday to talk about “efficiencies” and “innovations”, Mr Hegseth said.

Ahead of the meeting, the New York Times reported the tech billionaire would be briefed on plans for how the US would plan for a potential war with China – but this was denied by both Mr Musk and the president.

Mr Musk called the report “pure propaganda” and urged legal action against anyone leaking information.

The memo calling for an investigation said if it revealed information “identifying a party responsible for an unauthorised disclosure”, that information could be used to seek criminal prosecution.

Speaking at the White House after the meeting, Mr Trump said he did not want to show US plans for a potential war with China to anybody and hinted at Mr Musk’s potential conflict of interest.

“Elon has businesses in China, and he would be susceptible, perhaps, to that,” the president said.

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A New York Times spokesperson said leak investigations are “meant to chill communications between journalists and their sources and undermine the ability of a free press to bring out vital information that may otherwise be hidden”.

Earlier this month, homeland security secretary Kristi Noem pledged to step up lie detector tests on employees in an effort to identify those who may be leaking information about operations to the media.

While polygraph exams are typically not admissible in court proceedings, they are frequently used by federal law enforcement agencies and for national security clearances.