The unnamed Central Intelligence Officer once worked at the White House, the BBC quoted several US media outlets as saying.
A lawyer for the whistleblower warned that trying to identify the officer could place them "in harm's way".
This development comes after the complaint, which refers to a controversial phone call between Trump and Ukrainian President Volodymyr Zelensky on July 25, where the American leader pushes his counterpart to investigate corruption claims involving Joe Biden's son, Hunter, was released by the US House of Representatives Permanent Select Committee on Intelligence on Thursday.
"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," he said, describing Trump's personal lawyer, former New York Mayor Rudy Giuliani, as "a central figure in this effort", Efe news reported.
The whistleblower added that senior White House officials tried to "lock down" all details of the phone call.
He said that details of the call were stored in a "stand-alone computer system reserved for codeword-level intelligence information, such as covert action".
The complaint was addressed to Senator Richard Burr and Representative Adam Schiff, the respective chairmen of the Senate and House panels charged with overseeing intelligence, Efe news reported.
Democrats on Tuesday opened an impeachment inquiry against the Trump, accusing him of seeking foreign help in the hope of smearing Joe Biden and of using military aid to Ukraine as a potential bargaining tool.
Trump has denied any wrongdoing and dismissed the impeachment proceedings as a "hoax" and "another witch-hunt".
Meanwhile, an audio recording has emerged in which Trump demands to know who provided information to the whistleblower - and describes them as "close to a spy", the BBC reported.
The release of the whistleblower complaint on Thursday came as lawmakers on the House Intelligence Committee began to question President Trump's top intelligence official on the issue.
Acting National Intelligence Director Joseph Maguire had initially refused to share the complaint with Congress. But under questioning by the committee on Thursday, Maguire said he believed the whistleblower had acted in "good faith" and "did the right thing".
( With inputs from IANS )