President Donald Trump downplayed on Friday a complaint submitted by an intelligence whistleblower that reportedly involves Ukraine, claiming the complainant is partisan and his conversations with foreign leaders are “appropriate.”

But in a back-and-forth with reporters, he did not deny discussing former Vice President Joe Biden with Ukrainian President Volodymyr Zelensky in a July phone call — a potential subject for the complaint.

And he admitted he did not know the whistleblower’s identity, despite his accusation of partisanship.

It was a robust self-defense against accusations that remain, for now, veiled in mystery. An intelligence watchdog has said the claims are “urgent” and “serious,” but the acting top intelligence official has declined to provide them to Congress.

Trump dismissed them as another attempt to bring down his presidency. Speaking in the Oval Office, Trump called the story “ridiculous” and described the whistleblower as “just another political hack job.”

“It’s a partisan whistleblower. They shouldn’t even have information. I’ve had conversations with many leaders. They’re always appropriate,” Trump said alongside his Australian counterpart, who he was hosting for a state visit.

Asked whether he’d discussed Biden with Ukraine’s Zelensky during a phone call in late July, Trump said it “doesn’t matter what I discussed,” but insisted that someone should look into Biden.

“It was disgraceful, where he talked about billions of dollars he’s not giving to a certain country unless a certain prosecutor’s taken off the case,” Trump said, appearing to refer to January remarks when Biden discussed his interactions with Ukraine’s leadership when serving as vice president.

“The fake news,” Trump claimed,”doesn’t look into things like that.”

Trump’s remarks came a day after the New York Times and Washington Post reported that an intelligence whistleblower had submitted a complaint related to Trump’s interactions on Ukraine. Precise details of the accusation aren’t known, much to the chagrin of Democratic lawmakers, who have demanded more information.

Trump admitted Friday he did not know the whistleblower’s identity, and said he wasn’t even sure if it was his conversation with Ukraine’s leader that was the topic of the complaint.

But he nevertheless appeared defensive about his interactions with Zelensky, whom he will meet next week on the sidelines of the United Nations General Assembly.

Appearing in a rambling interview on CNN on Thursday evening, the President’s personal attorney Rudy Giuliani admitted he himself had discussed Biden with Ukraine’s leaders during a visit to the country.

That conversation has come under scrutiny from House investigators, who have demanded more information about Trump and Giuliani’s interactions regarding Ukraine and the Biden matter. That includes a transcript of Trump’s July phone call with Ukraine’s president.

Democrats are also looking for more information about the whistleblower’s complaint.

“There’s a real sense of urgency here since the Inspector General was so clear this is not something that can wait,” said House Intelligence Committee chairman Adam Schiff on Friday, a day after his panel was briefed behind closed doors by the inspector general.