US House Speaker Nancy Pelosi said Trump "abused his power for his own political benefit at the expense of our national security.” (AFP)

Top US Democrat Nancy Pelosi gave the green light to draft articles of impeachment against Donald Trump on Thursday, saying the president’s abuse of power “leaves us no choice but to act.”

By asking the House Judiciary Committee chairman to draw up the charges, Speaker Pelosi signaled that a formal vote on impeaching the 45th American president is all but assured.

With a majority of the Democratic-controlled chamber already expressing intent to back the divisive procedure, Trump is likely to become just the third president in US history to be impeached by the House of Representatives.

“Sadly, but with confidence and humility, with allegiance to our founders and a heart full of love for America, today I am asking our chairman to proceed with articles of impeachment,” Pelosi said in a televised statement.

Trump “has engaged in abuse of power, undermined our national security and jeopardized the integrity of our elections,” she said, adding that “the president leaves us no choice but to act.”

Pelosi’s address was short and somber. But America’s most powerful female politician, facing a grave, high-pressure moment of reckoning, concluded a follow-up press conference by showing flashes of anger when a reporter asked if she hated the president.

“I don’t hate anyone,” she fired back, pointing at the journalist in an extraordinary confrontation.

“I pray for the president all the time. So don’t mess with me when it comes to words like that.”

Pelosi did not announce the charges against Trump, but they could include abuse of power, obstruction of Congress and obstruction of justice.

“The president abused his power for his own political benefit,” Pelosi said, by withholding military aid and a White House meeting in exchange for Kiev’s commitment to investigate Joe Biden, his potential Democratic rival in the 2020 election.

“If we allow a president to be above the law, we do so surely at the peril of our republic,” added the speaker.

Accusing Democrats of seeking to remove him “over NOTHING,” Trump dared his opponents to press ahead with impeachment “now, fast” — so that he can have a “fair trial in the Senate” where his Republican Party holds power.

“The good thing is that the Republicans have NEVER been more united,” Trump tweeted. “We will win!”

The White House, which has refused to cooperate with the inquiry, said Democrats should be “ashamed” for pulling the impeachment trigger.

The process is expected to move rapidly from here on, with articles likely presented for a full House vote later this month after weeks of hearings.

Democrats do not want impeachment, and a subsequent Senate trial, to suck up too much political oxygen just as voting kicks off to determine their party’s presidential nominee for 2020.

On Wednesday, three constitutional scholars told the Judiciary Committee that the president’s actions seeking foreign interference in US elections were clear grounds for removal.

But one scholar, called by the Republicans to testify, told the panel there was “inadequate” evidence for impeachment.

Top House Republican Kevin McCarthy agreed.

No bribery, no extortion, no obstruction of justice, and no abuse of power,” he told reporters.

“Why are we going through this nightmare?”

Polling shows Americans are about evenly split on impeaching and removing Trump.

According to a FiveThirtyEight.com poll average, 46.8 percent of respondents support Trump’s impeachment and removal, versus 44.5 percent who do not.

The process has the potential to backfire on Democrats who face reelection in districts won by Trump, but Pelosi insisted she was making no political considerations going forward with impeachment.

“We are doing this in the right way,” she said. “We don’t take any glee in this at all. This is heartbreaking.”