President Trump admitted Sunday that he discussed Joe Biden in a phone call with newly elected Ukrainian President Volodymyr Zelensky in July, seemingly confirming reports that he discussed a potential investigation into a domestic political opponent with a foreign leader.

"The conversation I had was largely congratulatory, with largely corruption, all of the corruption taking place and largely the fact that we don't want our people like Vice President Biden and his son [contributing] to the corruption already in the Ukraine," Mr. Trump told reporters at the White House before departing on a trip to Texas.

The president's admission about his conversation about Biden with the current Ukrainian president is an extraordinary development in the unfolding dispute over a whistleblower complaint by a member of the intelligence community. The administration has refused to provide the complaint to Congress, but details about its contents have slowly emerged over the past week.

President Trump talks with reporters before leaving on Marine One on the South Lawn of the White House in Washington, Sunday, on Sept. 22, 2019. AP

House Speaker Nancy Pelosi demanded the administration provide the complaint to lawmakers, warning of a "grave new chapter of lawlessness" in a letter to congressional colleagues on Sunday. She called the standoff "an emergency that must be addressed immediately."

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The Washington Post reported Thursday that Ukraine was the subject of the whistleblower complaint, which a source familiar with the matter confirmed to CBS News. But the source said Ukraine was just "part" of the complaint, suggesting it included more than one element or allegation. The Wall Street Journal reported Mr. Trump urged Zelensky to investigate the Bidens eight times.

The president and his personal attorney Rudy Giuliani have accused Biden of acting inappropriately in 2016 by pushing Ukraine to oust then-prosecutor general Viktor Shokin, whom Western officials widely denounced as corrupt. The fired prosecutor had opened an investigation into a Ukrainian natural gas company whose board members included Hunter Biden, the former vice president's son.

The elder Biden said Saturday he had "never spoken to my son about his overseas business dealings," accusing the president of "violating every basic norm of a president" by pressuring Zelensky to investigate the son of a potential general election opponent.

"Trump's doing this because he knows I'll beat him like a drum. And he's using the abuse of power and every element of the presidency to try to do something to smear me," Biden said, calling on the president to release the transcript of the July call with Zelensky.

Democratic presidential candidate and former Vice President Joe Biden talks to reporters at the Polk County Democrats Steak Fry, in Des Moines, Iowa, on Saturday, Sept. 21, 2019. AP

Mr. Trump is scheduled to meet with Zelensky at the United Nations General Assembly in New York this week. He dismissed Biden's comments on Sunday.

"[Biden] made a lie when he said he never spoke to his son," the president said. "I mean, give me a break. He's already said he spoke to his son and now he said yesterday very firmly he didn't speak to his son. Of course you spoke to your son, so he made the mistake of saying he never spoke to his son."

Asked to react to the whistleblower complaint and the president's phone call, Secretary of State Mike Pompeo told "Face the Nation" that the pressure was justified, an unusual foray into domestic politics for the nation's top diplomat.

"If there was election interference that took place by the vice president, I think the American people deserve to know. We know there was interference in the 2016 election," Pompeo said. "And if it's the case that there was something going on with the [vice] president or his family that caused a conflict of interest and Vice President Biden behaved in a way that was inconsistent with the way leaders ought to operate, I think the American people deserve to know that."

John Kerry, the Democratic former secretary of state, told "Face the Nation" that the decision to push for the prosecutor's removal came from career diplomats in the State Department and was in line with the consensus in the administration at the time.

"You couldn't move forward to deal with Ukraine if it didn't end corruption. So, that was the focus," Kerry said. "It was professionals in the State Department and an ambassador who requested that we be involved to try to get a prosecutor out of the way who was not able to move. That was an administration policy. It was the professional diplomats who requested that we try to do that. So, I think there's no equivalency here. The president's just, as you know, throwing up a distraction."

The natural gas company in question was owned by an ally of former Ukrainian President Viktor Yanukovych, who was aligned with Russian President Vladimir Putin before being forced from office in 2014.

On Sunday, the president also brought up that the former vice president threatened to withhold funding from the country if it didn't remove Shokin. Mr. Trump referred to "what [Biden] said about the billions of dollars that he wouldn't give them unless they fired the prosecutor and then he bragged about how they fired the prosecutor and they got the money."

It is true that Joe Biden, while vice president, threatened to withhold aid from Ukraine unless it ousted Shokin and the Ukrainian parliament voted to do so in 2016. But there is no evidence presented that he wanted Shokin removed in order to stop Hunter Biden from being prosecuted, and Shokin's removal was hardly a surprise. For months he had been widely criticized by the U.S. and European powers for his failure to prosecute government officials and members of Parliament for corrupt actions taken during the Yanukovych administration.

And while an investigation into the company had been opened, according to Bloomberg, by the time Biden made his threat, "the probe into the company ... had been long dormant."

Biden himself has spoken openly about his conversation he had with the Ukrainians, describing the interaction at an event at the Council of Foreign Relations in January 2018.

"I said, 'I'm telling you, you're not getting the billion dollars,'" Biden said. "I said, 'You're not getting the billion. I'm going to be leaving here' in, I think it was about six hours. I looked at them and said, 'I'm leaving in six hours. If the prosecutor is not fired, you're not getting the money.' Well, son of a b***h. He got fired. And they put in place someone who was solid at the time."