Donald Trump Jr's exposure to the Mueller investigation stems from a meeting with a Kremlin-connected Russian lawyer promising damaging information on Hillary Clinton that he and Trump son-in-law Jared Kushner attended at Trump Tower in July 2016.
"Fake News reporting, a complete fabrication, that I am concerned about the meeting my wonderful son, Donald, had in Trump Tower", the president tweeted.
And Trump once again defended the June 2016 Trump Tower meeting in which his son met with a Kremlin-connected lawyer saying it was "totally legal" and that he didn't know about it.
While Trump has claimed since taking office that "no collusion" occurred between his campaign and Russia and that Mueller was conducting a "witch hunt", Trump's acceptance of Russian help has been out in the open since the final month of the 2016 campaign.
Some have argued that the Trump Tower meeting involved the illegal exchange of a "thing of value" with foreign nationals for campaign finance purposes, although the extent to which information sharing can legally constitute a "thing of value" is unsettled.
Trump Jr.'s testimony to Congress contained a similar defense as his father's Sunday tweet, indicating that he saw no reason not to accept a meeting that could yield important information about Clinton, even though he was told that it was part of an effort by the government of a hostile power.
Any legal battle over whether the president can be compelled to testify could go all the way to the U.S. Supreme Court, the lawyer, Jay Sekulow, said on ABC's "This Week".
To make it looks like there's something new here, the Times cites old statements, not by President Trump but by members of his team, that the meeting focused on subjects other than opposition research.
Trump, of course, claims to not knowing about the meeting, in spite of his involvement in the statement mentioned above.
He reiterated that he had no prior knowledge of the 20-minute meeting when it happened, adding that "it went nowhere".
Far from something that is "done all the time", Trump's admission would make him the first US presidential candidate in history to admit accepting campaign aid from the Russian government.
Trump Jr. and his attorney have insisted he has always told the truth.
'I don't represent Don Jr., but I will tell you I have no knowledge at all of Don Jr. being told that he's a target of any investigation, and I have no knowledge of him being interviewed by the special counsel, ' he said.
"The question is what law, statue or rule or regulation's been violated?"
One of the president's personal lawyers said on Sunday that if Trump is subpoenaed by the special counsel, his lawyers will attempt to quash it in court.
President Donald Trump singles out the media during his rally on August 2, 2018 at the Mohegan Sun Arena at Casey Plaza in Wilkes Barre, Pa. "They can also cause War!" In it, lawyers stated that Trump had dictated the statement written aboard Air Force One as it flew back from the G-20 summit in Germany. And at a trio of rallies, he escalated his already vitriolic rhetoric toward the media, savaging the press for unflattering coverage and, he feels, bias.