Democrats in the US charged aggressively into an impeachment investigation of president Donald Trump on Friday, ordering Secretary of State Mike Pompeo to turn over Ukraine-related documents and scheduling testimony for witnesses to alleged abuse of power by the US leader.
Three House committees gave Mr Pompeo one week to produce the documents, saying multiple State Department officials have direct knowledge of Mr Trump's efforts to enlist the Ukrainian government's help in his US domestic political campaign for re-election.
They also announced interviews scheduled with five State officials, including former ambassador to Ukraine Masha Yovanovitch, whom Mr Trump reportedly forced out earlier this year for resisting his efforts to pressure Kiev to probe Democratic rival Joe Biden.
"The Committees are investigating the extent to which President Trump jeopardised national security by pressing Ukraine to interfere with our 2020 election and by withholding security assistance provided by Congress to help Ukraine counter Russian aggression," they said.
House Speaker Nancy Pelosi declared that the impeachment investigation would move quickly, saying the evidence from an intelligence whistleblower's complaint against Mr Trump of abuse of power and an attempted cover-up was unambiguous.
"The clarity of the president's actions is compelling and gave us no choice but to move forward," Ms Pelosi said.
"This is about the national security of our country: The president of the United States being disloyal to his oath of office, jeopardising our national security, and jeopardising the integrity of our elections."
The White House was reeling, appearing not to have a strategy in place yet to counter the Democratic investigative onslaught after a week of fast-moving events rocked the foundations of Mr Trump's tempestuous two-and-a-half-year presidency.
In a series of tweets the president attacked Democrats - including Adam Schiff, the lawmaker named on Friday by Ms Pelosi to lead the impeachment probe - calling them liars.
In a video leaked from a private gathering Mr Trump held Thursday with US diplomats in New York, Mr Trump made clear he was battling for his survival.
"We're at war. These people are sick," Trump says in the video obtained by Bloomberg.
Support mounted for impeachment after the release of the anonymous whistleblower's complaint, reportedly made by a CIA analyst who had worked in the White House.
It accused Mr Trump of pressuring Ukraine's President Volodymyr Zelensky in a July 25 phone call to supply dirt on former vice president Joe Biden, the favourite to represent Democrats against Mr Trump in the 2020 presidential election.
The complaint also revealed that White House aides, alarmed at Mr Trump's implicit offer to release aid in exchange for Mr Zelensky's help, sought to hide the record of the call in a highly secure computer system normally used only for the country's most top-secret intelligence.
More than 300 high-level professionals from the national security community signed a letter supporting the impeachment investigation.
"President Trump appears to have leveraged the authority and resources of the highest office in the land to invite additional foreign interference into our democratic processes. That would constitute an unconscionable abuse of power," they said.
Meanwhile public support for impeachment jumped, according to two new polls. The Hill-HarrisX survey showed support increased by 12 points to 47 per cent, against 42 per cent opposed, while Politico's poll showed support up by seven points to 43 per cent, now equal to those opposed.
Democrats said articles of impeachment - formal charges - against Mr Trump could be completed in as soon as a month’s time and then swiftly debated and voted on in the House, where the party has a majority solid enough to ensure passage.
The case would then be handed to the Senate to try Mr Trump - who, for the moment, appears able to count on a Republican majority in the chamber to prevent his conviction and removal.
"We should move quickly but not hurriedly, and we should focus on this Ukraine call," Democrat Eric Swalwell, a member of the House Intelligence Committee, said on CNN.
"As a former prosecutor, I should tell you that cases are made much easier when the defendant cops to the act, and here the president is not denying what he said."
"We don't need to have a months-long hearing ... We have the president's own words, and we have his conduct after the fact," he said.