The person's identity is protected by US laws supporting officials

The whistleblower whose complaint has shaken the foundations of Donald Trump's presidency is a male officer of the Central Intelligence Agency who was seconded to the White House, the New York Times reported Thursday.

The man "was detailed to work at the White House at one point" but has since returned to the CIA, the Times said, citing three people familiar with his identity.

The complaint, which describes Trump using his powers to pressure the Ukraine government to find damaging information on Democratic political rival Joe Biden, "suggested he was an analyst by training and made clear he was steeped in details of American foreign policy toward Europe," the Times said.

He also was clearly knowledgable about Ukrainian politics and Washington's relations with Kiev, which Trump is accused of manipulating to gain advantage in next year's presidential election.

It was the first indication of the whistleblower's identity, other than previous statements saying it was either a man or a woman from the nearly million-strong intelligence community.

The person's identity is protected by US laws supporting officials who go through proper channels to report gross misconduct by their colleagues or superiors.

But the person is expected to testify soon behind closed doors in Congress, raising the prospect of exposure as more and more people learn their identity.