Democrats had "no choice" but to launch an impeachment probe into U.S President Donald Trump, House speaker Nancy Pelosi said Friday, adding Trump put national security in jeopardy with his attempts to get Ukraine to investigate political rival former vice-president Joe Biden.

Pelosi formally launched the impeachment inquiry earlier this week amid a confrontation between Congress and the White House over a whistleblower complaint regarding Trump's July 25 call with Ukraine's newly elected President Volodymyr Zelensky.

"Our members came to their own decisions in their own time about this. But when it was such a compelling national security issue, it's just – he gave us no choice," the house speaker said in an interview with MSNBC.

The whistleblower, who reportedly spoke to at least six U.S. government officials, concluded that Trump was "using the power of his office to solicit interference from a foreign country in the 2020 U.S. election," according to the text of the complaint released on Thursday.

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The complaint also described how White House officials removed an electronic record of Trump's call with Zelenskiy from the computer server where such records are normally kept to one reserved for highly classified intelligence matters.

Trump acknowledges he urged Ukraine to launch an anti-corruption probe against Biden – a front-runner in the race to take on the president in the 2020 election – and Biden's son.

To coordinate with Ukrainian officials on the investigation, Trump told Zelensky to liaise with both his personal lawyer Rudy Giuliani and Attorney General Bill Barr, leading Pelosi to accuse the Justice Department head of misconduct.

"He's going rogue," Pelosi said of Barr. "I think where they're going is a cover-up of the cover-up," Pelosi said. "To have a Justice Department to go so rogue – well they have been for a while and now it just makes matters worse."

Pelosi also criticized Acting Director of National Intelligence Joseph Maguire, who testified before the House Intelligence Committee on Thursday, for notifying the White House and Justice Department of the whistleblower complaint.

The law requires such complaints to be turned over to Congress. Maguire said he went to the White House first because he thought calls involving the U.S. president could be protected by executive privilege.

Pelosi also said Maguire "broke the law" by not going to Congress first.

Trump has said he exerted "no pressure" on Kiev, a claim echoed by Zelensky. But critics maintain that the president held up nearly 400 million U.S. dollars in military aid to Ukraine to pressure the Ukrainian leader.

Trump continued his attacks on one of his biggest Democratic critics in Congress, Adam Schiff, who is chairman of the House Intelligence committee that will lead impeachment proceedings, which he calls a witch hunt.

"I am calling for him to immediately resign from Congress based on this fraud!" Trump said on Twitter.

As of Friday, 223 Democrats – all but 12 – and one independent in the 435-seat House of Representatives support an impeachment inquiry, according to Politico.

(With input from Reuters, AFP)

(Cover: U.S. Speaker of the House Nancy Pelosi talks during her weekly press briefing on Capitol Hill in Washington, DC, the United States, September 26, 2019. /VCG Photo)