The FBI last month requested an interview with the whistleblower who made the complaint about President Trump’s July 25 phone call with Ukrainian President Volodymyr Zelensky and sparked the ongoing impeachment inquiry in the House, but no substantive discussions have taken place, a source familiar with the situation told Fox News on Wednesday.

The source said an agent from the bureau's Washington field office reached out to the unnamed whistleblower’s legal team about six weeks ago.

The source added that it was clear from the FBI that the whistleblower was not regarded as the target of any investigation -- but rather, a potential witness. It was not immediately clear what the FBI specifically might have been seeking.

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The source described the interaction between the FBI and the whistleblower's lawyers as "checking a box." The agent did not know the identity of the whistleblower and was not asking about threats against them, the source said, adding that it didn't appear to be an effort to intimidate or expose that person,

The whistleblower filed a complaint on Aug. 12 about Trump’s phone call weeks earlier with Zelensky. During the call, Trump pressed for investigations related to former Vice President Joe Biden, his son Hunter and their business dealings in that country, among other things.

A rough transcript of the call was released this past September by the White House. The House at the same time opened an impeachment inquiry centered on Trump’s effort to seek political investigations as the U.S. was withholding hundreds of millions of dollars in military aid from Ukraine.

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Trump has said he wanted to know the identity of the whistleblower. House Democrats have said they did not need to hear from the whistleblower as part of the impeachment inquiry and have heard now from multiple witnesses who, unlike the whistleblower, listened to the actual call between the two leaders.

U.S. whistleblower laws have existed to protect the identity and careers of people who bring forward accusations of wrongdoing by government officials. Lawmakers in both parties historically have backed those protections.

Fox News' Jennifer Griffin and Louis Casiano contributed to this report.