Senate Majority Leader Mitch McConnell on Friday urged President Donald Trump "not to worry" after the Republican-led Senate Intelligence Committee subpoenaed the president’s eldest son, Donald Trump Jr.

"I know the president's upset about that, but I think he ought not to worry about it. The chairman of the Intelligence Committee has already said the committee, when it reports, will find no collusion," McConnell told WHAS, a Kentucky radio station.

McConnell’s comments come one day after his GOP colleague – Sen. Richard Burr of North Carolina, who chairs the Senate Intelligence Committee, faced political backlash from members of his own party over his decision to subpoena Trump Jr.

Trump said on Thursday that he was "surprised” about the subpoena, adding that he "saw Richard Burr saying there was no collusion two or three weeks ago."

GOP Sen. Rand Paul took a major swipe at Burr, telling reporters that the subpoena is an “overzealous persecution of the president’s family” and that it couldn’t have happened “without Republicans being complicit in it.”

"At some point this is not about finding facts, this smacks of politics," Sen. John Cornyn, R-Texas, a Senate Intelligence Committee member, told reporters Thursday morning. "And I think we have an important job to do to try to keep the intelligence committee out of politics..."

"I can understand his frustration at being asked to come back after having cooperated for such a long period of time, seeing now that the Mueller report has concluded, sort of wondering what the purpose of this is," Cornyn said of Trump Jr.

Cornyn later said he was speaking about the congressional investigations in general, and not about Burr's decision to subpoena Trump Jr., adding the "committee’s been doing important work that’s been done on a bipartisan basis, and it really is about finding out what the facts are and what we need to do to prevent foreign interference in the future."

Burr remained tight-lipped on Capitol Hill, refusing to answer reporters’ questions on the decision to subpoena Trump Jr.

But McConnell defended the years-long work of the Intelligence Committee during his radio interview on Friday, commending the committee’s investigation into the 2016 election and Russian interference as bipartisan.

"This Intelligence Committee in the Senate, unlike the Intel Committee in the House, has not descended into partisan bickering. It's been a largely bipartisan effort. Chairman Burr has indicated that they'll be reporting very soon," McConnell said.

He added: "we ought to just take a deep breath and understand that this episode is coming to an end."

The top Democrat on the Intelligence Committee, Vice Chairman Mark Warner, D-Va., also came to Burr’s defense.

“Some of the criticisms out there are not the first time the chairman or I have received criticisms over this investigation,” Warner told reporters Thursday.

“I am proud of this committee because we're the only committee that is still bipartisan, still following the facts. And we're going to continue that process,” he said.

Trump Jr. has previously met with three congressional committees, including the Senate Intelligence Committee in December of 2017, with whom he met for more than nine hours as part of their investigation into Russian interference in the 2016 presidential election. He met with the Senate Judiciary Committee in September of 2017 for more than five hours and with the House Intelligence Committee for more than eight hours in December of 2017.

It is unclear why the committee wants Trump's son to return to testify. He has not publicly responded to the subpoena.

A source close to Trump Jr. said there was an agreement between the president’s son and the committee that he would only have to come in and testify once as long as he was willing to stay for as long as they’d like, which the source said he did.

In a separate interview with Fox News’ Sean Hannity on Thursday night, McConnell predicted the Senate Intelligence Committee’s investigation “is going to have a happy ending.”

“I understand the president’s frustration here. But I think that this is just a blip," he said. "I think that the case is closed. I think that the controversy has been concluded.”