After revealing he didn't know who the individual was, President Donald Trump attacked the US spy agency whistleblower at the center of a complaint against him as "partisan" and defended the "beautiful conversation" he had with an unnamed foreign leader on Friday.

"I don't know the identity of the whistleblower, I just hear its a partisan person meaning it comes out from another party," Trump said. "It was a totally appropriate conversation. It was actually a beautiful conversation."

On Wednesday, the Washington Post reported that Trump was the subject of a whistleblower complaint filed with the inspector general of the intelligence community back in August — and it was of "urgent concern."

The New York Times recently reported that the complaint is said to involve Trump and Ukraine.

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After revealing he didn't know who the individual was, President Donald Trump attacked the US spy agency whistleblower at the center of a complaint against him as "partisan" and defended the "beautiful conversation" he had with the foreign leader on Friday.

"I don't know the identity of the whistleblower, I just hear its a partisan person meaning it comes out from another party," Trump said. "It was a totally appropriate conversation. It was actually a beautiful conversation."

On Wednesday, the Washington Post reported that Trump was the subject of a whistleblower complaint filed with the inspector general of the intelligence community back in August — and it was of "urgent concern."

Read more: A major whistleblower complaint at the US's top spy agency involves a Trump phone call with a 'promise' to a foreign leader

The individual, who has not been publicly identified, was apparently concerned with a phone call Trump made with a foreign leader. It was said to include "a promise" that was so deeply disturbing to the individual that they lodged a formal complaint.

The Post also reported that Trump had interacted with several foreign leaders in the five weeks before the complaint was filed, including Russian President Vladimir Putin and North Korean leader Kim Jong-Un. But Trump initiated a call with Putin, the only one he's known to have spoken on the phone with.

Read more: The US's top spy agency just dropped a big hint that an 'urgent' whistleblower complaint involves Trump or someone close to him

The complaint is said to involve Trump and Ukraine, according to The New York Times. Back in July, Trump told the new Ukrainian president Volodymyr Zelensky that US-Ukraine ties could be improved if the country investigated corruption more forcefully.

And some of Trump's allies — like his personal lawyer Rudy Giuliani — have pushed the Ukrainian government to look into the dealings of Trump's political rivals, which include former Vice President Joe Biden.