A Russian American lobbyist and veteran of the Soviet military said Friday that he attended a June 2016 meeting between President Trump’s oldest son and a Kremlin-connected lawyer.

The presence of Rinat Akhmetshin adds to the potential seriousness of the Trump Tower gathering that is emerging this week as the clearest evidence so far of interactions between Trump campaign officials and Russian interests.

And it underscores how, despite Donald Trump Jr.’s pledge this week to be “transparent,” new details about the encounter continue to become public amid investigations by Congress and a special counsel into alleged collusion between Russia and the Trump campaign.

Emails released this week show that Trump Jr. believed he was meeting with a Russian government lawyer who would provide damaging information about Democrat Hillary Clinton as part of a Russian effort to assist his father’s presidential campaign. He was joined at the meeting by Jared Kushner, President Trump’s son-in-law, and Paul Manafort, then a top campaign aide — but Trump Jr. said this week that nothing came of the discussion.

The attendance of Akhmetshin, who says he holds U.S. and Russian citizenship and who has been accused by some U.S. critics of having links to Russian spy services, also appears to tie the Trump Tower meeting to a broader effort underway at the time to influence U.S. policy toward Russia.

Akhmetshin says he has never had ties to Russian intelligence, and he and lawyer Natalia Veselnitskaya have both said their efforts were not coordinated with the Russian government. Kremlin spokesman Dmitry Peskov told ­reporters Friday that the government was not familiar with Akhmetshin.

But in the same period that he was meeting with Trump campaign officials, Akhmetshin was also orchestrating a Capitol Hill lobbying effort that coincided with one of the Kremlin’s top priorities — to scale back U.S. sanctions imposed on Russia by Congress for human rights violations.

Akhmetshin told The Washington Post on Friday that he did not know how the Trump Tower meeting was set up. He said that he had lunch with Veselnitskaya that day a few blocks from Trump Tower and that she asked his advice on what to say at the session.

“She said, ‘Why don’t you come with me?’ ” he recalled.

He said that Veselnitskaya, who was representing a Russian businessman who had been sued by U.S. authorities in New York, had found what she believed to be violations of Russian law by a Democratic donor. Akhmetshin added that the Russian lawyer described her findings at the meeting and left a document about them with Trump Jr. and the others.

In an interview Friday evening, an attorney for Trump Jr., Alan Futerfas, again dismissed the notion that the meeting was significant. He said recalling attendees at the session was difficult because of the amount of time that had passed — and the lack of significance attached to the conversation. “The frustrating part of all this for me is that this meeting occurred 13 months ago,” he said. “There is no record, no list of who was there. It was not a memorable meeting for anyone. Now 13 months later, everyone expects we should have a perfect recollection.”

But while the Russians were granted a high-level audience with the Trump campaign, their efforts were setting off alarms in some corners of Washington.

(Thomas Johnson/The Washington Post)

Veselnitskaya was rebuffed after pushing to testify at a House hearing that took place days after the June 9, 2016, Trump Tower meeting.

House Foreign Affairs Committee Chairman Edward R. Royce (R-Calif.) rejected an attempt by the Russian team and its allies to screen a ­Russian-made documentary designed to undermine the arguments for a 2012 sanctions law, according to GOP congressional staffers who spoke on the condition of anonymity.

The Russians argued that the Magnitsky Act, named for a lawyer who died at age 37 in a Moscow prison after accusing Russian officials of a massive tax fraud, was based on a false story.

In retaliation for the passage of the law, Russia had halted the adoption of Russian children by American families. Veselnitskaya and her lobbying team would present their efforts in Congress and at Trump Tower as an emotionally powerful effort to end the prohibition on adoptions and help children.

They found an ally in Rep. Dana Rohrabacher (R-Calif.), who has in recent years become an advocate for warmer U.S.-Russia relations. Rohrabacher attempted to organize a hearing featuring critics of the sanctions — an effort that was also thwarted by Royce, according to the congressional staffers.

In a statement, Royce did not specifically address his efforts to block the anti-sanctions advocates but acknowledged that he and Rohrabacher have “sharp disagreements on policy.”

Rohrabacher was not available for comment Friday, but a spokesman, Ken Grubbs, acknowledged deep differences on Kremlin-

related policies between the two Republicans. “They are very good friends, and they have very strong disagreements on Russia,” Grubbs said.

The events unfolding on Capitol Hill and at Trump Tower in June 2016 followed a series of interactions a few months earlier in Moscow that may have played a role in shaping the lobbying efforts. In April 2016, Rohrabacher led a small congressional delegation to Moscow. During the trip, Rohrabacher’s spokesman confirmed, Rohrabacher met with a top Russian prosecutor who provided him documents making a case that the Magnitsky story was a fraud.

[Analysis: Another shoe drops in the White House’s burgeoning Russia scandal]

Akhmetshin said he became involved in the lobbying effort in late 2015 after he was introduced to Veselnitskaya by a Russian public relations manager he declined to identify.

Veselnitskaya told the Wall Street Journal in Moscow on Friday that although she had exchanged information with the Russian prosecutor’s office, her ­efforts were not undertaken on the government’s behalf.

Akhmetshin said that he thought her arguments had merit and arranged for a nonprofit organization that hired U.S. lobbyists and consultants to press her case before Congress. The group was funded, he said, by Veselnitskaya’s client, Denis Katsyv, and friends of his in Russia.

Akhmetshin was a controversial figure. In a letter this spring to U.S. government officials, Sen. Charles E. Grassley (R-Iowa) described Akhmetshin as a person who “apparently has ties to Russian intelligence.”

Akhmetshin said he never worked as an intelligence agent, but he did say he was drafted as a teenager and served for two years in a unit of the Soviet military that had responsibility for law enforcement issues as well as some counterintelligence matters. He immigrated to the United States in 1993 and gained citizenship in 2009.

“I was not an intelligence officer. Never,” he said.

In the spring of 2016, as the presidential race was heating up, Akhmetshin and lobbyists he hired sought meetings on Capitol Hill to make their case against the sanctions law. Akhmetshin hired former Democratic congressman Ron Dellums, along with a team of lobbyists from the law firm of Cozen O’Connor.

Steve Pruitt, a business colleague speaking on Dellums’s behalf, said his involvement was brief and ended when he determined that Congress was unlikely to change the law.

In June, after visiting Trump Tower in New York, Veselnitskaya came to Washington to lend a hand in the lobbying effort.

She attended a meeting of the team at the downtown offices of Cozen O’Connor, where she spoke at length in Russian about the issues but confused many in the room, who had not been told previously about her involvement, according to several participants.

A spokesman for Cozen said the firm had been hired by the nonprofit. But in a statement, the firm said that the role and involvement of the Russian lawyer was “not at all clear.”

While Veselnitskaya was not allowed to testify in Congress, she did secure a prime, front-row seat for a June 14 hearing in the House on Russia-related issues.

Her high-profile spot in the room gained notice this week with the circulation of a photo in which she looms over the shoulder of former U.S. ambassador to Russia Michael McFaul, an adviser to President Barack Obama and a witness before the panel. Some conservative blogs this week have said the photo suggests she had accompanied McFaul and was a Democratic plant.

In fact, her seat had been reserved for her by a Republican consultant with close ties to the Trump campaign.

Lanny Wiles, whose wife, Susie, was then chairing the Trump campaign in Florida, said in an interview that he came early to scout out the seat and was there at the request of Akhmetshin, with whom he was working as a consultant on the sanctions-related adoption issue.

Lanny and Susie Wiles both said she was unaware of his role in the lobbying effort. Lanny Wiles said he was unaware that the Russian lawyer whose seat he was saving had just days earlier met with Trump Jr.

“I wasn’t part of it,” Susie Wiles said.

Alice Crites contributed to this report.