Trump denies knowing whistleblower's identity, calls controversy 'political hack job'

President Donald Trump on Friday denied knowing the identity of a whistleblower who filed a formal complaint about a call the president had earlier this summer with a foreign leader, but attacked the person as "partisan" and called the unfolding controversy "just another political hack job."

"I do not know the identity of the whistleblower," Trump said during a meeting with Australian Prime Minister Scott Morrison in the Oval Office Friday morning. "I've had conversations with many leaders. They're always appropriate. Always appropriate. At the highest level they are always appropriate."

Asked by a reporter if the call in question was one he had July 25 with the president of Ukraine, Trump claimed he didn't know but he then characterized that conversation as "beautiful."

The call the whisteblower has complained about involved Ukraine, multiple sources familiar with the matter told ABC News.

Trump did not name Ukrainian President Volodymyr Zelensky in several tweets earlier Friday taking issue with with news reports about a call he said he had with "a certain leader," saying "there was nothing said wrong, it was pitch perfect!".

"It's a ridiculous story. It's a partisan whistleblower," he said. "And anything I do, I fight for this country. I fight so strongly for this country. It's just another political hack job."

Trump was asked whether the discussion was about former Vice President Joe Biden, the current front-runner in the Democratic presidential primary. The president said "it doesn't matter what I discussed," but later suggested that someone should look into Biden.

"It doesn't matter what I discuss, but I will say this: Somebody ought to look into Joe Biden's statement, because it was disgraceful where he talked about billions of dollars that he's not giving to a certain country unless a certain prosecutor is taken off the case," Trump asserted. "So somebody ought to look into that. And you wouldn't, because he's a Democrat. And the fake news doesn't look into things like that. It's a disgrace."

According to a readout released from the White House, Trump spoke with Zelensky on July 25 "to congratulate him on his recent election."

A more extensive readout from the Ukrainian president's office, however, noted that the two also spoke about "investigations into corruption cases that have hampered interaction between Ukraine and the U.S.A."

The president's personal lawyer, Rudy Giuliani, has publicly and privately urged in recent months for Ukrainian officials to investigate ties between Biden's diplomatic efforts in the country and any connections between his son's business ventures.

Leaving a campaign stop in Cedar Rapids, Iowa, on Friday, Biden blasted Trump.

“Not one single credible outlet has given any credibility to his assertions, not one single one," Biden said. "So, I have no comment except the president should start to be president."

In his tweets Friday morning, Trump attacked the Democratic chairman of the House Intelligence Committee, Rep. Adam Schiff, who's demanding details of the whistleblower complaint.

"The Radical Left Democrats and their Fake News Media partners, headed up again by Little Adam Schiff, and batting Zero for 21 against me, are at it again! They think I may have had a “dicey” conversation with a certain foreign leader based on a “highly partisan” whistleblowers ... statement," Trump tweeted.

"Strange that with so many other people hearing or knowing of the perfectly fine and respectful conversation, that they would not have also come forward. Do you know the reason why they did not? Because there was nothing said wrong, it was pitch perfect!" Trump added.

DNI Inspector General Michael Atkinson in a Sept. 9 letter to the House Intelligence Committee noted that the complaint rose to a level of "urgent concern" and "appeared credible" enough to warrant congressional notification.

The DNI's general counsel and the Department of Justice, however, have disputed that characterization of the complaint, resulting in a constitutional showdown between members of Congress and the Trump administration regarding matters of potentially privileged material.

House Speaker Nancy Pelosi on Friday warned that if the complaint about the president’s communications with a foreign leader have merit, then Trump “is stepping into a dangerous minefield with serious repercussions for his Administration and our democracy.”

"The President and Acting DNI’s stonewalling must end immediately, and the whistleblower must be provided with every protection guaranteed by the law to defend the integrity of our government and ensure accountability and trust,” Pelosi, D-Calif., wrote in a statement. “We will continue to follow the facts and explore every possible option to ensure the American people get the truth.”

ABC News' John Santucci, Rachel Scott and Alexander Mallin contributed to this report