President Donald Trump on Tuesday confirmed reports that his administration froze nearly $400 million in aid to Ukraine. But he gave a new reason for doing so: He said he wanted European countries to contribute money, too, and did not want the U.S. to do so alone.

The freeze came before a July phone call in which he reportedly pressured the Eastern European nation's leader to investigate the family of political rival Joe Biden, the former vice president.

"As far as withholding funds, those funds were paid," Trump said. "They were fully paid. But my complaint has always been — and I'd withhold again, and I'll continue to withhold until such time as Europe and other nations contribute to Ukraine, because they're not doing it."

"Very important, I want other countries to put up money," he added. "I think it's unfair that we put up the money. Then other people call me. They said, 'Oh, let it go.' And I let it go. But we paid the money, the money was paid."

He said he wants Germany, France and other nations to contribute more funds.

"And that's been my complaint from the beginning," he said.

Trump's remarks come amid revelations surrounding the president's apparent push to have the Ukrainian government investigate Biden's son, Hunter Biden, who had business dealings in the country. The late July discussion between Trump and Ukrainian President Volodymyr Zelensky has been scrutinized following a whistleblower complaint by a member of the U.S. intelligence community that media reports said was tied to the call between the two leaders. The administration is refusing to turn that complaint over to Congress.

On Monday, The Washington Post and other media outlets reported that Trump instructed his chief of staff to place a hold on about $400 million in military aid for Ukraine in the days before a late July phone call with Zelensky. The White House labeled the reporting as untrue.

But in the weeks before the existence of the whistleblower complaint became public knowledge, the Trump administration froze the military aid to Ukraine for unclear reasons. Then, just before Democrats revealed the existence of the whistleblower complaint, the administration released the hold on Ukrainian military aid.

The episode has led to an increased impeachment push among House Democrats. By mid-morning Tuesday, more than 150 House Democrats — nearly two-thirds of the 235-member caucus — now back some type of impeachment action in light of the burgeoning Ukraine scandal. More than a dozen lawmakers have announced such support since reports emerged about the president's conversation with Zelensky.

On Sunday, House Speaker Nancy Pelosi, D-Calif., threatened a "new stage of investigation" if the Trump administration and acting Director of National Intelligence Joseph Maguire fail to provide the whistleblower complaint to Congress. Maguire is scheduled to testify before the House Intelligence Committee on Thursday.

Maguire and the national intelligence inspector general, Michael Atkinson, are also set to appear before the Senate Intelligence Committee behind closed doors Thursday afternoon. Pelosi has called an all-caucus meeting for 4 p.m. Tuesday that is expected to cover impeachment.

Trump has teased the possibility he may release a transcript of his phone call with Zelensky, a move that several Republicans have publicly pushed him to make.

On Saturday, Ukrainian Foreign Minister Vadym Prystaiko said he didn't think Trump pressured Zelensky during the phone call. Trump and Zelensky are set to meet face to face this week on the sidelines of the United Nations General Assembly session in New York.

Speaking to reporters ahead of his speech to the United Nations Tuesday, Trump called the ratcheting up of impeachment talk "ridiculous" and a "witch hunt," before insisting that his call with Zelensky "was perfect."

Trump has admitted to talking about Biden with Zelensky, but denied putting any pressure on the Ukrainian leader.

"I put no pressure on them whatsoever," he said. "I could have. I think it would probably, possibly have been OK if I did. But I didn't. I didn't put any pressure on them whatsoever."

For months, Trump and his personal attorney Rudy Giuliani have sought to have Ukraine probe the Bidens — an effort aided by the State Department.

It centers on the former vice president's 2016 call, widely backed by the international community, for Ukraine to crack down on corruption. That included a push to remove a Ukrainian prosecutor, Viktor Shokin, who was seen as ineffective and was later removed by the country's Parliament. One of the cases that Shokin was investigating involved Burisma Holdings, a natural gas company, whose board at the time included Biden's son.

Earlier this year, Bloomberg News, citing documents and an interview with a former Ukrainian official, reported the Burisma investigation had been dormant for more than a year by the time Biden called for the crackdown on corruption. The then-Ukrainian prosecutor general told the news agency he found no evidence of wrongdoing by Biden and his son. And PolitiFact reported it found no evidence to "support the idea that Joe Biden advocated with his son's interests in mind."