For months, President Donald Trump and his aides have forcefully rejected any suggestion that they sought or received help from Russia to win last year’s election.

But the release on Tuesday of a 2016 email exchange in which the president’s eldest son welcomed the assistance of a “Russian government lawyer” offered the clearest contradiction of the White House’s denials — marking an escalation in the controversy that has engulfed the Trump presidency.

The email exchange was aimed at setting up a June 2016 meeting between Donald Trump Jr. and a Kremlin-connected lawyer who was said to have damaging information about Democratic candidate Hillary Clinton. The meeting at Trump Tower also was attended by Jared Kushner, the president’s son-in-law, and then-campaign Chairman Paul Manafort.

During the email exchange, Trump Jr. was told by an intermediary that the “high level” information he would be offered about Clinton was “part of Russia and its government’s support for Mr. Trump,” and would be “highly useful for your father.”

The younger Trump appeared to relish the opportunity. “If it’s what you say I love it especially later in the summer,” he wrote back.

Trump Jr. posted the exchange on Twitter, saying he was revealing the correspondence “in order to be totally transparent,” although the New York Times reported that the disclosure came after the newspaper informed him that it had reviewed the emails and intended to publish their content.

During an interview scheduled to air on Tuesday night on Fox News Channel’s Hannity show, Trump Jr. said that the meeting came when “things are going a million miles per hour” in the campaign and that nothing concrete resulted.

“In retrospect I probably would have done things a little differently,” Trump Jr. said, adding: “For me, this was opposition research. They had something, you know, maybe concrete evidence to all the stories I’d been hearing about, probably underreported for years, not just during the campaign, so I think I wanted to hear it out.”

But rather than stemming the scrutiny, Trump Jr.’s disclosures on Tuesday seemed to complicate matters further for the White House and undercut past efforts by the president to rebut allegations that his campaign colluded with the Kremlin.

A spokesman for the president’s lawyer has said that Trump was not aware of the meeting and did not attend.

On Fox, Trump Jr. said he did not tell his father about the meeting, saying, “There was nothing to tell.”

The email exchange showed clearly that Trump Jr. — a key figure in his father’s campaign — had reason to understand that he was accepting the meeting as a way to channel to his father’s campaign information directly from the government of a nation hostile to the United States.

The revelation, coming amid investigations by Congress and a special counsel, sparked immediate calls by Democrats for the meeting participants to testify under oath and raised questions about legal jeopardy that Trump Jr. and other associates could face.

The revelation also could heighten pressure on Republicans, many of whom on Tuesday either dismissed the significance of the Trump Jr. email exchange or declined to comment.

“Anytime you’re in a campaign and you get an offer from a foreign government to help your campaign, the answer is ‘no,’ ” said Sen. Lindsey Graham, S.C., one of the few GOP lawmakers to offer criticism, adding that Trump Jr. “definitely” must testify as part of investigations of Russia’s election meddling.

The White House on Tuesday offered a brief defense of Trump Jr., with deputy press secretary Sarah Huckabee Sanders reading a statement from the president in which he said his son “is a high-quality person and I applaud his transparency.”

Sanders referred most questions to lawyers for Trump and his son but relayed that the president is frustrated that Russia “continues to be an issue” and declined to answer a question about whether the president is now aware of Russia’s efforts to help his campaign.

U.S. intelligence agencies have concluded that Russian President Vladimir Putin directed a campaign to assist Trump, including the release of hacked emails stolen from Democratic officials.

Natalia Veselnitskaya, the Russian lawyer who took part in the meeting, denied in an interview on Tuesday that she had represented the Russian government, suggesting that she sought the meeting on an entirely different subject: Russian adoptions.

“I did not have an assignment from the Kremlin, there were no orders from the government,” Veselnitskaya said, adding that “someone in America really wants to overthrow their president.”

The meeting occurred at a critical time for the Trump campaign. The New York businessman was securing the Republican nomination but was widely considered a long shot to defeat the more organized and politically experienced Clinton.

The email came from Rob Goldstone, a music publicist who represented Emin Agalarov, whose father, Aras Agalarov, is a major real estate developer close to Putin.

“Emin just called and asked me to contact you with something very interesting,” Goldstone wrote to Trump Jr. “The Crown prosecutor of Russia met with his father Aras this morning and in their meeting offered to provide the Trump campaign with some official documents and information that would incriminate Hillary and her dealings with Russia and would be very useful to your father.”

It is not clear who Goldstone was referring to in his mention of the “Crown prosecutor.”

There is no such position in the Russian government.

“This is obviously very high level and sensitive information but is part of Russia and its government support for Mr. Trump — helped along by Aras and Emin,” Goldstone wrote.

Goldstone offered to send the information directly to the elder Trump but said that because it was “ultra sensitive,” he wanted to contact Trump Jr. first.

Trump Jr. appears to have forwarded the exchange to Kushner and Manafort. And he wrote that he had invited the two fellow campaign advisers to the meeting.

“It will likely be Paul Manafort (campaign boss) my brother in law and me,” Trump Jr. wrote. A person close to Manafort who was not authorized to speak publicly said Manafort did not read the entire chain. Goldstone did not respond on Tuesday to requests for comment on the email exchange. He confirmed that he has hired an attorney, Bob Gage, to handle Russia-related inquiries.

Scott Balber, a New York lawyer retained by Emin and Aras Agalarov, denied that Goldstone’s emails accurately outlined the origins of the meeting.

He said that Emin Agalarov is an acquaintance of Veselnitskaya and that she asked him if he could secure a meeting for her with Trump officials.