Members of the US Congress first saw a whistleblower complaint against Donald Trump that led
. A Democrat described it as "disturbing" while the Republican said it was "alarming."
The complaint alleges a controversial telephone conversation between Mr Trump and the Ukrainian president, according to US media.
Recent developments come as Acting Director of US Intelligence, testifying on the matter.
The account of Joseph Maguire for the complaint of an unnamed scout would be carefully considered when he appeared before members of the House Intelligence Committee later on Thursday.
The contents of the complaint are still classified, but the top Democrat in the United States Sen. Chuck Schumer called for his immediate release.
During a news conference Wednesday night, President Trump again dismissed the impeachment procedure as "fraud" and "witch hunt."
- Breakup of phone call behind impulse for Trump's impeachment. Joe Biden's son, Mr Trump's eventual contender in next year's presidential election. There is no evidence of any wrongdoing by Bidens.
In a tweet on Wednesday, Mr. Biden accused President Trump of "abuse of power."
The complaint against the president was filed ̵
It is alleged that it affects not only Mr Trump's call with President Zelensky, but also the manner in which the records of the conversation were handled by White House officials, the New York Times reported.
"I found the allegations deeply disturbing. I also found them very plausible," said Adam Schiff, Democratic chairman of the House Intelligence Committee.
"I think this. what this brave individual has done has revealed serious misconduct, "he said, referring to the whistleblowers. "We will do everything we can to protect you.
Lawmakers said they hoped to hear the whistle at one point, but no meeting was scheduled.
Democrat committee member Mike Quilly called the complaint" deeply disturbing "until senator. Ben Sass, a Republican member of the Senate Intelligence Committee, said there were "real troubling things."
"Republicans don't have to go around wagons alone," he said.
a member of the Republican Committee on the House Intelligence Committee said he did not believes that the complaint will compromise Mr Trump, adding: "I have not seen anything that bothers me."
Mr Sumer, calling for the contents of the complaint to be published, said: "The public has the right to read the complaint against
What about the impeachment claim?
The Democrats accuse Mr. Trump of seeking someone else's help in order to anoint Joe Biden and use the aid as a potential negotiating tool.
Under the US Constitution, a president may be prosecuted for "treason, bribery or other high crimes and misdemeanors" – a procedure that could result in removal from office.
In July, Mr Trump froze Ukraine's military assistance, but he insisted that it was not used to pressure the new government in Kiev.