US President Donald Trump has defended his son, who is under fire for meeting with a Russian lawyer during the 2016 presidential campaign, saying most "would have taken that meeting in a heartbeat".

The US president's comments come as Donald Trump Jr faces criticism over meeting the lawyer, who allegedly said she had "compromising" information on Hillary Clinton that could help with the 2016 election campaign.

"No I didn't know about [the meeting]", Trump told the Reuters news agency on Wednesday.

"I didn't know, until a couple of days ago, when I heard about this," he said.

On Tuesday, Trump Jr released an email chain from June 2016 that shows him discussing plans to hear damaging information on his father's political rival, Clinton, which was described by a British publicist who arranged the meeting as "part of Russia and its government's support" for Trump.

Trump: 'Most would take that meeting'

Trump Jr, Jared Kushner and Paul Manafort met the Russian lawyer, Natalia Veselnitskaya, on June 9, 2016.

Trump Jr has said the meeting was a "waste of time", but has come under fire amid ongoing investigations into Trump's alleged ties with Russia during the election.

Veselnitskaya has said she never had information on Clinton.

READ MORE: US Senate begins hearing on Russia involvement in US elections

During Wednesday's interview with Reuters, the US president defended his son by repeatedly saying anyone in his position would have done the same thing.

"If you got a call and said, 'Listen I have information on Hillary and the DNC', or whatever it was they said, most people are going to take that meeting, I think", he said.

The president also described the campaign as a "wild time" during which his team met with many people.

'Colluding' with the Kremlin

Democrats and some Republicans have called the revelations regarding the June 2016 meeting "disturbing" and proof the Trump campaign "colluded" with the Kremlin.

Congress and a special prosecutor, or counsel, are currently investigating allegations that Russia meddled in the 2016 presidential election and tipped the results in Trump's favour, accusations the Kremlin denies.

On Wednesday, Trump called the allegations a "hoax made up by the Democrats", a statement he has made in the past.

Also on Wednesday, California Democratic Senator Brad Sherman filed an article of impeachment against Trump, accusing the US president of obstructing investigations into Russian meddling in the election, in part by firing former FBI Director James Comey.

While the article does formally start the impeachment process, the effort is likely to stall in the Republican-controlled congress.

READ MORE: NYT - Trump Jr knew of Kremlin efforts to aid campaign

Meanwhile, Democrats on the House Judiciary Committee questioned the decision by the Trump administration's justice department to settle a money-laundering forfeiture case with a Russian real estate investment firm that has ties to Veselnitskaya.

The letter sent by House Judiciary ranking member John Conyers and other Democrats asked Attorney General Jeff Sessions whether Veselnitskaya had been involved in settlement negotiations between the Russian firm and the Department of Justice.

The House Democrats also asked whether Trump, his family, or other aides contacted the justice department about its case against the Russian firm.

The Trump administration is yet to respond to the letter.

Al Jazeera's Heidi Zhou-Castro, reporting from Washington, DC, said the development is "a lot to unpack".

"But what it boils down to is that this is a troubling development that asks whether there is yet another link in this very tangled web that seemingly connects Trump's very inner circle with Russia," Zhou-Castro said.