Trump Jr has been under scrutiny by Mueller and his team for his alleged role in organizing a meeting in June 2016 at Trump Towers with a Russian lawyer offering dirt on his father's opponent Hillary Clinton.
"This was a meeting to get information on an opponent, totally legal and done all the time in politics - and it went nowhere", Trump said on Twitter.
Zeitz described Trump "calling me a third-rate lawyer", explaining he knew it was a good sign because it meant "I had gotten to him".
Sunday's tweet was Trump's clearest statement yet on the objective of the meeting, which has become a focal point of Mueller's investigation even as the president and his lawyers try to downplay its significance and pummel the Mueller probe with attacks.
On Sunday, Trump also defended tariffs he has imposed on imports into the U.S.
Trump lawyer Jay Sekulow nevertheless attempted to rationalize the 2016 meeting as legal in an interview Sunday on ABC's This Week.
Sekulow said that the president had the authority under Article II of the U.S. Constitution to stop any investigation conducted by the Department of Justice.
However, in January, Trump's legal team, which included Sekulow, wrote a memo to Mueller saying that the president did dictate a response to the New York Times' story about the meeting on behalf of his son.
Trump has repeatedly denied collusion with Russian Federation or any other wrongdoing.
Russian President Vladimir Putin has denied allegations by US intelligence agencies that his government meddled and Trump denies collusion, describing the Mueller investigation as a political witch hunt that should be shut down. "You have to look at what laws, rules, regulations, statutes are purportedly violated here". "I believe it's in the best interest of the president and of the United States of America and the American people for that investigation to run the course, for all the truth to come out".
The President this week has for the first time said that Attorney General Jeff Sessions "should stop" the Mueller probe.
"I had bad information at that time and made a mistake in my statement", Sekulow said. "This is obviously very high level and sensitive information but is part of Russian Federation and its government's support for Mr. Trump". American intelligence officials say Russian Federation is targeting the November congressional elections, which will determine whether or not Republicans keep control of both chambers of the U.S. Congress.
US President Donald Trump has yet again tweeted about his personal legal issues in a way he perhaps shouldn't have.
Also, if any Americans aided in disseminating the Russian hacked data, then they could be roped in as co-conspirators in Mueller's indictment of 12 Russian intelligence officers (GRU) for hacking the DNC, DCCC, and Hillary Clinton's presidential campaign during the 2016 election and leaking through DCLeaks and Guccifer 2.0.