Ahead of meeting a Russian lawyer believed to offer compromising information about Hillary Clinton, Donald Trump Jr. was informed that the material was part of Kremlin's effort to aid his father's candidacy, a report by The New York Times said.
The information was sent in an email by Rob Goldstone, a publicist and former British tabloid reporter who helped broker the June 2016 meeting, three sources with knowledge of the email told The New York Times on Monday.
In a statement on Sunday, Donald Trump Jr. acknowledged that he was interested in receiving damaging information about Clinton, but gave no indication that he thought the lawyer might have been a Kremlin proxy.
Goldstone's message indicates that the Russian government was the source of the potentially damaging information. However, it does not elaborate on the wider effort by Moscow to help the Trump campaign, the sources said.
There is also no evidence to suggest that the promised damaging information was related to Russian government computer hacking that led to the release of thousands of Democratic National Committee (DNC) emails.
The meeting between Donald Trump Jr. and Russian lawyer, Natalia Veselnitskaya was also attended by the President's campaign chairman at the time, Paul J. Manafort, and his son-in-law, Jared Kushner.
It took place on June 9, 2016, less than a week before it was widely reported that Russian hackers had infiltrated DNC's servers.
The New York Times first reported on the existence of the meeting on Saturday.
Donald Trump Jr.'s lawyer Alan Futerfas said his client had done nothing wrong but pledged to work with investigators if contacted.
"In my view, this is much ado about nothing. During this busy period, Robert Goldstone contacted Don Jr. in an email and suggested that people had information concerning alleged wrongdoing by Democratic Party front-runner, Hillary Clinton, in her dealings with Russia," he told The New York Times on Monday.
"Don Jr.'s takeaway from this communication was that someone had information potentially helpful to the campaign and it was coming from someone he knew. Don Jr. had no knowledge as to what specific information, if any, would be discussed."
In response to The New York Times' report, Donald Trump Jr. said in a series of tweets on Monday evening that he "happy to work with the (Senate) committee to pass on what I know".
The Federal Bureau of Investigation and Congress are currently investigating alleged Russian meddling in last year's US election, including whether any of President Donald Trump's associates colluded with the Kremlin to influence the result.