WASHINGTON (Reuters) - The whistleblower who said U.S. President Donald Trump pressured Ukraine to investigate Democratic rival Joe Biden is a CIA officer and at one point was assigned to work at the White House, two sources familiar with the probe into his complaint confirmed on Thursday.

A woman holds a sign about whistleblowers in a cafe near U.S. President Donald Trump’s motorcade as he attends a campaign fundraiser nearby in New York, U.S. September 26, 2019. REUTERS/Jonathan Ernst

The New York Times first identified the whistleblower as a CIA officer, which Reuters has independently confirmed.

Mark Zaid, a Washington lawyer who represents the whistleblower at the center of an impeachment inquiry into Trump, declined to confirm the identity or occupation of his client.

“Publishing details about the whistleblower will only lead to identification of someone, whether our client or the wrong person, as the whistleblower. This will place this individual in a much more dangerous situation, not only in their professional world but also their possible personal safety,” Zaid told Reuters.

A CIA spokesman referred inquiries to the office of the Intelligence Community Inspector General, which declined to comment.

Democrats in the House of Representatives this week launched a formal impeachment inquiry into Trump, based largely on the whistleblower’s complaint that Trump pressed Ukrainian President Volodymyr Zelenskiy in a telephone call to investigate Biden and his son Hunter, who had business interests in Ukraine.

Joe Biden, who was vice president during Barack Obama’s presidency, is a top contender for the Democratic nomination to challenge Trump in the November 2020 presidential election.

The whistleblower alleged, in a report released earlier on Thursday, that Trump abused his office in pressuring Ukraine to investigate Biden, and that the White House tried to “lock down” evidence about that conduct by putting a summary of the call into a separate electronic system used to store and handle sensitive classified information.

Democratic House Speaker Nancy Pelosi said the report showed that the Republican president “has been engaged in a cover-up all along.”

Trump has denied wrongdoing and accuses Democrats of launching a “witch hunt” against him.

“What ... Democrats are doing to this country is a disgrace and it shouldn’t be allowed. There should be a way of stopping it, maybe legally through the courts,” Trump told reporters.