Sen. Richard Blumenthal, D-Conn., fired back at President Trump on Monday morning after the president called him a "phony Vietnam con artist."

"Mr. President: Your bullying hasn't worked before and it won't work now. No one is above the law," Blumenthal tweeted Monday morning. "This issue isn't about me—it's about the Special Counsel's independence and integrity," he continued.

Blumenthal appeared on CNN on Monday morning and said he was concerned Trump is trying to "politicize" the Justice Department after the agency announced Friday it is reviewing subpoena policies for reporters.

"That's a chilling effect on the press and on whistleblowers, and on information that doesn't involve classified data or disclosures, but in fact may be just embarrassing or unwelcome," he said.

Blumenthal also said that without a free press, the public wouldn't know about meetings Trump's transition team held with Russian officials. Meetings members of the Trump campaign team and his family had with Russian officials are part of the Justice Department's investigation into Russian meddling in the 2016 election.

Trump took to his Twitter account to criticize Blumenthal after the interview.

"Interesting to watch Senator Richard Blumenthal of Connecticut talking about hoax Russian collusion when he was a phony Vietnam con artist!" Trump tweeted. "Never in U.S. history has anyone lied or defrauded voters like Senator Richard Blumenthal. He told stories about his Vietnam battles and conquests, how brave he was, and it was all a lie."

"He cried like a baby and begged for forgiveness like a child," the president continued. "Now he judges collusion?"

A decade ago, Blumenthal said numerous times he served in Vietnam when he never did. Instead, the Connecticut Democrat received five military deferments.