In the call, Trump pushed Zelensky to investigate corruption claims involving Democratic presidential hopeful Joe Biden's son Hunter, according to the whistleblower's complaint released by House Intelligence Committe on Thursday.
The whistleblower describes how the transcript of the Trump-Zelensky call was moved to a computer system managed by the National Security Council Directorate for Intelligence Programs, in a partially redacted appendix attached to his complaint.
This move was concerning to some officials, who shared their concerns internally that this was an "abuse of the system", the US media reported.
"In the course of my official duties, I have received information from multiple US government officials that the President of the US is using the power of his office to solicit interference from a foreign country in the 2020 US election," the whistleblower wrote in the complaint dated August 12.
"This interference includes, among other things, pressuring a foreign country to investigate one of the President's main domestic political rivals. The President's personal lawyer, Rudolph W. Giuliani, is a central figure in this effort. Attorney General (William P.) Barr appears to be involved as well," it said.
The complaint says that White House officials were so alarmed by Trump's conduct that they sought to limit access to the written record of the phone call.
House Intelligence Committee Chair Adam Schiff called the White House transcript of the call between Trump and the Ukrainian President the "most graphic evidence yet that the President of the US has betrayed his oath of office."
Biden said a rough transcript of the conversation released on Wednesday shows that the President betrayed his oath of office.
Democrats opened an impeachment inquiry against Trump on Tuesday, accusing him of seeking foreign help in the hope of smearing Biden and of using military aid to Ukraine as a potential bargaining tool.
US lawmakers also questioned acting National Intelligence Director Joseph Maguire over the issue. He had initially refused to share the complaint with Congress.
Testifying before the House Intelligence Committee, Maguire said he was "not political" and cited his oath to protect the US Constitution.
He said the whistleblower's complaint centered around a phone call between Trump and a foreign leader - a kind of conversation that is "typically subject to executive privilege".
He said executive privilege is a "privilege that I do not have the authority to wave."
"Because of that, we were unable to immediately share the details of the complaint with this committee," he added.
Maguire said that he believes both the whistleblower who filed the complaint against President Trump and the inspector general who handled it "acted in good faith".
Trump has dismissed the impeachment proceedings as a "hoax" and a "witch-hunt".
( With inputs from IANS )