Donald Trump Jr has said his “sirens didn’t go up” before he met with a Russian lawyer promising dirt on Hillary Clinton, in his first interview since he released a damning series of emails.

The eldest child of US president Donald Trump spoke to Fox News after tweeting an email exchange between himself and publicist Roy Goldstone that showed them arranging a meeting with Russian attorney Natalia Veselnitskayato to discuss potentially incriminating information about Democratic nominee Hillary Clinton.

Mr Trump Jr told host Sean Hannity he “probably would have done things differently”, after the revelation incited widespread criticism, with some prominent US Democrats suggesting his actions amounted to “treason”.

Mr Trump defended his intentions in arranging the meeting during the 2016 election campaign, arguing that at the time he viewed meeting with Ms Veselnitskaya as “opposition research”.

“I didn’t know if there was anything behind it, I can’t vouch for the information. Someone sent me an email. I can’t help what someone sends me. I read it, I responded accordingly,” he told Mr Hannity.

“My takeaway when all of this was going on is that someone has information on our opponent.”

Russian attorney Natalia Veselnitskaya said President Trump’s aides wanted dirt on Mrs Clinton “so badly”. Photo: AAP

In an interview with NBC on Tuesday, Ms Veselnitskaya claimed Mr Trump Jr, along with Jared Kushner and Paul Manafort, who also attended the meeting, wanted information on Mrs Clinton “so badly”.

“All I knew was that Mr Donald Trump Jr was willing to meet with me. I could recognise the young gentleman who was only present in the meeting for only the first seven to 10 minutes. And then, he stood up and left the room. It was Mr Jared Kushner. And he never came back, by the way.”

Ms Veselnitskaya denied ever working for the Russian government.

Despite Mr Trump Jr’s lawyer saying his client “did nothing wrong”, Senator Tim Kaine, an attorney and Mrs Clinton’s vice-presidential running-mate, said his actions could amount to treason.

“When he was approached with this idea he should have turned it over to law enforcement immediately,” the Democrat told CNN.

“We are now beyond obstruction of justice in terms of what’s being investigated … This is moving into perjury, false statements and even, potentially, treason.”

US attorney Nick Akerman, who worked on the Watergate case, told New York Post reporter Gabby Morrongiello, “there’s no question this is treason”.

“It shows there was collusion,” Mr Akerman told The Independent. “That they were willing to take that information from the Russian government, even if it was information stolen by the security forces of Hillary Clinton.”

Jacob Neiheisel, Assistant Professor in Political Science, at the State University of New York, told The New Daily the emails are “probably as close as you can get to a smoking gun in this case”.

“I’ve long said that this is precisely the kind of evidence that would be necessary to make this case more than just circumstantial,” Prof Neiheisel said.

“Nevertheless, I think it is probably pretty early to start talking about the ‘T’ word.

“There is, however, a better case to be made for some kind of violation of campaign finance law, where the receipt of something of value from an outside entity could be seen as a ‘contribution in-kind’.”

Trump Jr has not testified under oath regarding his connections with Russia. He said his father had no knowledge of the meeting.

In a statement on Tuesday (US time), the President applauded his son for his “transparency”.

Watch: Donald Trump Jr calls Veselnitskaya meeting ‘a waste of time’

.@DonaldJTrumpJr on meeting with Russian attorney: "It was such a nothing, I wouldn't have remembered the meeting." #Hannity pic.twitter.com/K072AvmKKQ

— Fox News (@FoxNews) July 12, 2017

– with reporting by Rachel Eddie