US House Speaker Nancy Pelosi said she has instructed the House Judiciary panel to draft articles of impeachment against President Donald Trump over his effort to pressure Ukraine to investigate a political rival.
Pelosi delivered the historic announcement on Thursday as Democrats push toward a vote to impeach Trump, possibly by Christmas.
She said she was authorising the drafting of articles of impeachment "sadly but with confidence and humility".
"The President's actions have seriously violate the Constitution," Pelosi said.
Pelosi made the remarks a day after the Judiciary Committee held a hearing in which three constitutional law experts called by Democratic lawmakers said Trump had engaged in conduct that represents impeachable offenses under the Constitution.
"The President's actions have seriously violate the Constitution," Pelosi said.
A fourth expert called by Republican lawmakers called the Democratic-led impeachment inquiry rushed and flawed.
The House Intelligence Committee this week submitted findings from its inquiry into Trump's push for Kiev to launch an investigation related to former US Vice President Joe Biden, a top contender for the 2020 Democratic presidential nomination.
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Trump also wanted Ukraine to look into the discredited theory that Ukraine, not Russia, meddled in the 2016 US election.
Democrats have accused Trump of abusing his power by withholding US$391 million in security aid to Ukraine - a US ally facing Russian aggression - to pressure Ukrainian President Volodymyr Zelenskiy to announce the investigation.
Trump has denied any wrongdoing and called the impeachment investigation a hoax.
After Pelosi delivered her statement on Thursday, Trump accused Democrats of trying to impeach him over "two totally appropriate (perfect) phone calls with the Ukrainian President".
The Do Nothing, Radical Left Democrats have just announced that they are going to seek to Impeach me over NOTHING," Trump tweeted.
"They already gave up on the ridiculous Mueller "stuff," so now they hang their hats on two totally appropriate (perfect) phone calls with the Ukrainian President....
"This will mean that the beyond important and seldom used act of Impeachment will be used routinely to attack future Presidents. That is not what our Founders had in mind."
