U.S. House of Representatives Speaker Nancy Pelosi asked lawmakers Thursday to draft articles of impeachment against President Donald Trump. 

The step marks a dramatic escalation in the House’s hitherto impeachment probe, and comes just one day after the Judiciary Committee carried out its first public hearing into the matter.

"The president leaves us no choice but to act," Pelosi said in televised remarks. "Sadly, but with confidence and humility, with allegiance to our founders and a heart full of love for America, today I am asking our chairmen to proceed with Articles of Impeachment."

The House's investigation is centered on Trump's multiple requests to Ukrainian President Volodymyr Zelensky to declare criminal investigations into leading Democratic presidential candidate Joe Biden and his son, Hunter, as well as claims it was Ukraine, not Russia, who meddled in the 2016 election.

Also at issue is the holdup of $400 million in congressionally-appropriated military aid to Ukraine and whether Trump conditioned the release of the assistance and a possible Oval Office meeting with Zelensky on the Ukrainian president publicly announcing the investigations.

Just hours before Pelosi's announcement Trump said if House Democrats "are going to impeach me, do it now, fast, so we can have a fair trial in the Senate, and so that our Country can get back to business."

"We will have Schiff, the Bidens, Pelosi and many more testify, and will reveal, for the first time, how corrupt our system really is," Trump tweeted. 

He later continued to defend his July 25 telephone call with Zelensky in which pressed the Ukrainian leader for a "favor," repeating his defense that it was "perfect." Trump asserted late Wednesday that he was referring to a favor for the United States, not him personally. 

The House Judiciary Committee announced its next hearing will be held Monday, and will feature presentations from impeachment investigators. Its first hearing included testimony from legal scholars, nearly all of whom said Trump's actions rise to the level of "high crimes and misdemeanors" -- the constitutional bar for impeachable offenses. 

It is unclear when the House will vote on any articles of impeachment, but in the likely event that at least one passes the chamber the charges would move on to the Senate where they would be tried in the Republican-held body. 

It is unlikely that any article would garner the necessary two-thirds majority needed to convict Trump and remove him from office. In all, Republicans hold 53 seats in the 100-member Senate.