Trump said Wednesday he was "very surprised" by the subpoena issued to his son, though it was issued more than two weeks ago, according to a source familiar with the matter.
It's the first known subpoena of a member of Trump's immediate family and a new sign that the Senate panel is continuing with its own two-year-long investigation, even after the release of special counsel Robert Mueller's report and Republican Senate Majority Leader Mitch McConnell's call from the Senate floor on Tuesday to move on.
Mueller's team of prosecutors said there was a "reasonable argument" that Trump Jr. had violated campaign finance laws but concluded they did not believe they could obtain a conviction.
Trump Jr. testified before the committee in 2017 and testified multiple other times before Congress.
Major Powers, Israel React To Tehran's Partial Suspension Of Nuclear Deal
A waiver also enabled Iran to ship excess heavy water to Oman for storage, from where it could be sold to foreign customers. However, once a country enriches uranium to around 20pc, scientists say the time needed to reach 90pc is halved.
41, has testified voluntarily in private once to the committee, and was peppered with questions about a June 9, 2016 meeting in Trump Tower in NY that he and other senior Trump campaign officials had with a Russian lawyer offering dirt on Democratic presidential candidate Hillary Clinton.
The sources said the senators want to question Trump Jr. about testimony he gave to the Senate Judiciary Committee in September 2017 which was subsequently contradicted by Michael Cohen, Trump's former lawyer who started his prison sentence this week in part for lying to Congress.
Asked if he would block his son from complying with the subpoena, Trump added, "We'll see what happens".
"[Donald Trump Jr.] has already spent dozens of hours testifying in front of congressional committees. It's time to focus on ISSUES, not investigations", tweeted House Minority Leader Kevin McCarthy, R-Calif.
The panel's investigation, led by Burr, has been running for more than two years, and the committee has interviewed numerous same witnesses who spoke to special counsel Robert Mueller's team.