During an appearance on Fox News's Sunday Morning Futures, Senator Lindsey Graham brushed off the Senate Intelligence Committee's attempts to subpoena Donald Trump Jr. to give further testimony regarding efforts to build a Trump Tower in Russia.

“If I were Donald Trump Jr.’s lawyer, I would tell him you don’t need to go back into this environment anymore,” Graham said. “You’ve been there for hours and hours, and nothing being alleged here changes the outcome of the Mueller investigation. I would call it a day.”

The subpoena came as the Senate Intelligence Committee attempts to wrap up its own investigation, and mostly concerns conflicting testimony from Trump’s former attorney and fixer, Michael Cohen, and Trump Jr.

The son of the president told the panel in 2017 that he was only “peripherally aware” of efforts to build a Trump Tower in Moscow, a claim that Cohen subsequently refuted.

"Cohen also recalled briefing Donald Trump Jr. in the spring, a conversation that Cohen said was not 'idle chit chat' because Trump Tower Moscow was potentially a $1 billion deal,” reads a pertinent line from Special Counsel Robert Mueller’s investigation.

The controversy surrounding the Moscow plan also stems from President Donald Trump’s own admissions that he “had no business dealings with Russia” while campaigning for office, despite his company working to secure the deal. Also under scrutiny is Trump Jr.’s 2016 meeting with Russian nationals, including lawyer Natalia Veselnitskaya, who claimed to have “dirt” on Clinton.

During his appearance on Fox News, Graham said Cohen’s track record for lying under oath meant that his testimony shouldn’t be taken seriously. In November 2018, Cohen pleaded guilty to lying to the Senate Intelligence Committee and House Intelligence Committee regarding the proposed Trump Tower Moscow deal. Cohen later said he regretted lying and had “misplaced” trust in Trump.

“Anything based on what Michael Cohen’s said is worthless testimony,” Graham, reiterating his previous criticism of Trump’s former confidant. “Michael Cohen is a worthless witness.”

The summons was issued weeks ago by the intelligence panel’s chairman, Sen. Richard Burr, a conservative from North Carolina in his third term. The lawmaker has a reputation for generally keeping a low profile compared to some of his colleagues—but the subpoena’s revelation thrust him under the spotlight. While

“All I can say is Richard Burr is a very good friend, he’s trying hard to appear bipartisan,” Graham said.

Other conservative lawmakers haven’t been so congenial. During an appearance on a radio show on Sunday, Senator Rand Paul suggested the summons was an intentional “perjury trap.”

“This is not a friendly maneuver. This is an adversarial maneuver to bring him in under oath,” the Kentucky elected said. And the Democrats will try to trip him up and get him to make some kind of mistake.”

Correction: A previous version of this article incorrectly referred to "Sunday Morning Futures" as a Fox Business Network program. In fact, it airs on Fox News.