US President Donald Trump has rushed to his son's defence after a Senate panel ordered that Donald Trump Jr testify as part of its investigation into Russia election interference.
It was the first known legal summons issued by Congress to a member of the president's family to force testimony in the ongoing investigation.
Senate Intelligence Committee Vice Chair Mark Warner, D-Va., who leads the panel with Republican Chairman Richard Burr of North Carolina. Source: AAP
"I was very surprised," Trump told reporters about the Senate Intelligence Committee's subpoena to the eldest of his five children.
The order by the Republican-run committee that is known for its bipartisanship comes after Special Counsel Robert Mueller decided there was insufficient evidence to charge Trump with any crime related to possible conspiracy to collude with the Russians.
"My son is a very good person, he works very hard. The last thing he needs is Washington DC. I think he'd rather not ever be involved," Trump said.
It comes as two House Democrats on Thursday joined activists at the US Capitol who presented Congress with signatures of 10 million people calling on lawmakers to begin impeachment proceedings against President Trump.
"We are holding in our hands 10 million reasons for being here today," progressive congressman Al Green said, as he and first-term congresswoman Rashida Tlaib held up a flash drive.
Trump Jr has already testified at length to the committee, and was "totally exonerated by Mueller," his father said.
"For my son, after being exonerated, to now get a subpoena to go again, to speak again after close to 20 hours after telling everybody that would listen about a nothing meeting? Yeah, I'm pretty surprised."
The 41-year-old Don Jr testified voluntarily in private once to the committee, and was peppered with questions about a June 9, 2016 meeting in Trump Tower in New York that he and other senior Trump campaign officials had with a Russian lawyer offering dirt on Democratic presidential candidate Hillary Clinton.
It is also believed he was quizzed about his knowledge or involvement in a project to build a Trump Tower in Moscow that Mr Trump pursued even as he ran for president in 2016.
In Senate Judiciary Committee testimony, Mr Trump Jr said he was only "peripherally aware" of the potential deal.
But Mr Mueller's report states that the chief handler of the project, Mr Trump's now-jailed personal lawyer Michael Cohen, briefed Trump Jr about the project "on multiple occasions."
The president said part of his surprise stemmed from seeing Republican Senator and intelligence committee chairman Richard Burr tell US media that there was no evidence of collusion between Russian operatives and Mr Trump or his campaign to influence the 2016 election.
Mr Burr has not spoken publicly about the latest subpoena, or whether Trump Jr might invoke his constitutional right to not testify.
Republican committee member Marco Rubio, when asked about Mr Trump Jr, said the panel was "leaving nothing unchecked" in its investigation.
But Senator John Cornyn sounded unenthusiastic about hauling Trump Jr in for more questioning.
"We've been at this for about two years," he said. "I think we know pretty much everything we are going to learn, and I think we ought to wrap it up."
