WASHINGTON, Sept. 24 -- U.S. House Speaker Nancy Pelosi announced Tuesday the initiation of a formal impeachment inquiry against President Donald Trump over the latter's controversial phone call with the Ukrainian president.

"Today, I'm announcing the House of Representatives is moving forward with an official impeachment inquiry," said the Democratic congresswoman from California in a speech, as she concluded a closed-door meeting with the House Democratic Caucus.

Citing Trump's admission this week that he talked about Democratic presidential candidate Joe Biden during the July 25 phone call with Ukrainian President Volodymyr Zelensky, Pelosi said "the actions of the Trump presidency revealed the dishonorable fact of the president's betrayal of his oath of office, betrayal of our national security, and betrayal of the integrity of our elections."

Pelosi said she will direct six House committees to proceed with their investigations into Trump "under that umbrella of impeachment inquiry."

"The President must be held accountable. No one is above the law," she said.

Trump responded immediately to Pelosi's announcement, taking to Twitter and calling the inquiry "a presidential harassment."

The president said the Democrats "never even saw the transcript of the call," adding their decision to impeach him is "a total Witch Hunt!"

Earlier on Tuesday, Trump said he authorized the release of the full transcript of the phone call between him and his Ukrainian counterpart.

The president tweeted from New York, where he was attending the United Nations General Assembly session, that he has "authorized the release tomorrow of the complete, fully declassified and unredacted transcript" of the phone call. "You will see it was a very friendly and totally appropriate call," he added.

Also on Tuesday, the president confirmed media reports that he had ordered the halt of almost 400 million U.S. dollars in military aid to Ukraine one week ahead of the phone call, but he told reporters that the suspension was because European countries did not pay their fair share to help the Eastern European country defend its national security, adding that the aid from the United States was already paid.

The Wall Street Journal reported Friday that Trump pressed Zelensky about eight times in the phone call to seek information about business dealings between Democratic presidential candidate Joe Biden's son, Hunter Biden, and a Ukrainian gas company. The information could potentially be damaging to Biden senior's White House bid.

"No pressure and, unlike Joe Biden and his son, NO quid pro quo!" Trump said in the tweet announcing the release of the transcript.

The presidential conversation between Washington and Kiev is at the center of a whistleblower complaint filed in mid-August by an unidentified intelligence official, alleging that Trump interacted inappropriately with a foreign leader and made an unspecified "promise."

Senate Minority Leader Chuck Schumer, Democrat from New York, said Tuesday his chamber voted unanimously in support of the content of the whistleblower complaint being provided to Congress.

"The Senate by unanimous consent passed my resolution calling for the whistleblower complaint to be provided to Congress as required by law," Schumer tweeted.

"That means every GOP Senator supports the whistleblower report being immediately provided to the Senate and House Intel Committees," he added. Acting Director of National Intelligence Joseph Maguire has been withholding the material from congressional committees investigating the scandal.

The Hill, in a Monday report, cited a congressional official as saying Maguire and Michael Atkinson -- inspector general of the intelligence community with which the complaint was filed -- are both expected to testify before the Senate Intelligence Committee later this week.

Maguire is scheduled to appear before the House Intelligence Committee on Thursday, the report added.

On the other side of the aisle, Republicans in both chambers denounced Pelosi's announcement. House Minority Leader Kevin McCarthy called on the Democrats to "put the public before politics."

"Speaker Pelosi happens to be the speaker of this House but she does not speak for America when it comes to this issue. She cannot decide unilaterally what happens here," McCarthy told reporters Tuesday. "They have been investigating this President before he even got elected," he added, referring to the Democrats.

Senate Majority Leader Mitch McConnell, for his part, called the impeachment inquiry a "rush to judgment" by "Washington Democrats."

"This rush to judgment comes just a few hours after President Trump offered to release the details of his phone conversation with President Zelensky," the Republican from Kentucky said in a statement. "It comes despite the fact that committee-level proceedings are already underway to address the whistleblower allegation through a fair, bipartisan, and regular process."

In an attempt to contain the fallout of the scandal, McConnell said Monday that lawmakers should handle the issue through bipartisan cooperation.

"I believe it's extremely important that their work be handled in a secure setting with adequate protections in a bipartisan fashion, and based on facts rather than leaks to the press," he said.