Donald Trump Jr. refuses to comply with Senate subpoena if they ask about Trump Tower meeting or Moscow: CNN
Donald Trump Jr. (Fox News)

President Donald Trump's son Don Jr. was subpoenaed by the Republican-led Senate Intelligence Committee to answer questions about the discrepancies in his previous testimony and Robert Mueller's report.

Mueller refused to bring charges against the younger Trump because he was too ignorant to know what he was doing wasn't ethical or legal, CNN reported Monday.

Two sources told CNN that Trump Jr. is "balking at answering anymore questions" about the Trump Tower meeting and about building Trump Tower Moscow.

"Don Jr. doesn't want to have a complete do-over of his testimony from Dec. 2017," said CNN's Kara Scannell. "Now, the issues here is that we're learning some new information that Chairman Richard Burr (R-NC) of the Senate Intelligence Committee has told some of his members and colleagues that they initially began these conversations with Donald Trump Jr.'s team back in December. That there were tentative agreements for Don Jr. to come in and meet with them in April, but then those talks fell apart after it was clear that the Senate intelligence committee didn't want to place any limitations on their discussions with Donald Trump Jr."

"If I were Donald Trump Jr.'s lawyer, I would tell him, you don't need to go back into this environment anymore," Sen. Lindsey Graham (R-SC) said last week. "You have been there for hours and hours and hours, and nothing being alleged here changes the outcome of the Mueller investigation."