Washington (CNN) President Donald Trump had been briefed on the whistleblower complaint that's now at the heart of the House impeachment inquiry when he released military aid to Ukraine in September, The New York Times reported Monday, citing two people familiar with the matter.

The people told the Times that lawyers from the White House counsel's office briefed Trump on the complaint and explained that they were attempting to ascertain whether they were legally obligated to give it to Congress.

News of Trump's knowledge of the complaint before his decision to release the security assistance underscores a key question at the heart of the impeachment inquiry about whether the aid was tied to Trump's wish for Ukraine to investigate former Vice President Joe Biden and his son, Hunter.

A hold had been placed on the Ukraine aid at the beginning of July, and the agencies were notified at a July 18 meeting that it had been frozen at the direction of the President, a week before the Trump-Zelensky call.

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