A formal inquiry into whether US President Donald Trump should be impeached will be launched after House Speaker Nancy Pelosi accused him of breaching his constitutional responsibilities.
The Democratic-controlled House will examine whether Mr Trump sought Ukraine's help to smear former vice president Joe Biden, the favourite for the 2020 Democratic presidential nomination.
“Today, I'm announcing the House of Representatives is moving forward with an official impeachment inquiry," Ms Pelosi said on Tuesday.
"I'm directing our six committees to proceed with their investigations under that umbrella. The president must be held accountable.
“He is asking a foreign government to help him in his campaign. That is a betrayal of his oath of office."
Mr Trump said earlier that on Wednesday he would release a complete transcript of the call with Ukrainian President Volodymyr Zelenskiy.
Ms Pelosi has faced mounting pressure from Democrats to move ahead with impeachment proceedings.
Mr Trump tweeted from the UN General Assembly in New York that he would release a transcript of his conversation with Mr Zelenskiy, and that it would show “a very friendly and totally appropriate call".
“This is nothing more than a continuation of the greatest and most destructive witch hunt of all time,” he wrote.
Mr Trump confirmed on Tuesday he had withheld nearly $400 million in aid to Ukraine but denied accusations he did so to pressure Mr Zelenskiy to start an investigation that would damage Mr Biden.
Meanwhile, US House intelligence committee chairman Adam Schiff said his panel was in contact with an attorney representing the whistleblower from intelligence who reported Mr Trump's phone call with the Ukrainian president.
The intelligence staff member would like to testify this week, Mr Schiff said on Twitter.
He said the whistleblower's lawyer was talking with the acting director of national intelligence about how to proceed.