President Trump issued a brief statement standing by his eldest son following the release Tuesday of emails detailing a meeting with a Russian attorney last year, as the messages fueled critics' claims of "collusion" as well as calls for Donald Jr. to testify before Congress.

White House Deputy Press Secretary Sarah Huckabee Sanders read the statement from the president during Tuesday’s off-camera press briefing, before referring questions on the matter to Donald Trump Jr.'s outside counsel.

“My son is a high-quality person and I applaud his transparency,” the statement said.

In this photo taken on Tuesday, Nov. 8, 2016, Kremlin-linked lawyer Natalia Veselnitskaya speaks to a journalist in Moscow, Russia. President Donald Trump's eldest son changed his account of the meeting he had with a Russian lawyer during the 2016 campaign over the weekend, saying Sunday July 9, 2017, that Natalia Veselnitskaya told him she had information about Clinton. A statement from Donald Trump Jr. one day earlier made no mention of Clinton. (Yury Martyanov /Kommersant Photo via AP) RUSSIA OUT (AP)

Sanders had adamantly defended the president's son a day earlier. But the emails, which Donald Trump Jr. released on Twitter earlier Tuesday, quickly have caused new headaches for the administration.

What was described as the "entire email chain" showed the discussions that led up to a 2016 meeting between the president's son and a Russian attorney who supposedly claimed to have information that could “incriminate” Hillary Clinton during the presidential campaign.

The email from the contact who set up the meeting with attorney Natalia Veselnitskaya described the offer as “part of Russia and its government's support for Mr. Trump.” Trump son-in-law Jared Kushner and then-campaign chairman Paul Manafort also attended.

Sanders told reporters that the president learned of the meeting in the last couple of days, and did not know the last time he spoke to his son.

DONALD TRUMP JR. RELEASES 'ENTIRE EMAIL CHAIN' REGARDING RUSSIAN MEETING

Trump Jr. released a new statement, along with the email chain, on Twitter, explaining he was releasing the messages “in order to be totally transparent.” The New York Times suggested on Twitter that Trump Jr. only shared images of the emails after “he was told NYT was about to publish the contents of the emails.”

Some top-ranking lawmakers now are seeking Trump Jr.'s testimony. Sen. Dianne Feinstein, D-Calif., top Democrat on the judiciary committee, said Trump Jr. and others should "come before the committee, in open session, as soon as possible."

Senate Republican Whip John Cornyn, R-Texas, when asked about the intelligence committee's plans to reach out to the president's son, said he couldn't "imagine a world" where that doesn't happen.

Sanders pushed back when challenged during Tuesday's briefing on the president's claim of “transparency.”

Sanders added: “The willingness to [answer questions] is fully transparent and open to do so through the correct process, whether that’s through special counsel or anyone beyond that.”

When also asked about the relationship between President Trump and Vice President Pence, Sanders replied: “There is absolutely no distance between the president and the vice president.”

Sanders told reporters Trump and Pence spoke on Tuesday, but did not know if they spoke about the meeting between Trump Jr. and Veselnitskaya. Pence’s press secretary, Marc Lotter, separately told Fox News on Tuesday that “the Vice President was not aware of the meeting.”

DONALD TRUMP JR. 'DID NOT COLLUDE WITH ANYBODY,' WHITE HOUSE SAYS

“He is not focused on stories about the campaign, particularly stories about the time before he joined the ticket,” Lotter said.

President Trump, through his outside counsel, also has denied knowing about or attending the meeting.

“I stand by everything I said yesterday,” Sanders assured reporters on Tuesday. “I think the president is frustrated with ... the fact that this continues to be an issue and he would love for us to be focused on things like economy, health care, tax reform, and infrastructure and that’s where his mind is, and what he’d like to be discussing.”

A day earlier, Sanders said Trump Jr. he “did not collude with anybody to influence the election.”

Trump Jr. accepted the June 9, 2016 meeting offered by publicist Rob Goldstone, who identified Veselnitskaya as “the Russian government attorney who is flying over from Moscow.”

Revelations and details surrounding the meeting have given Democrats further ammunition in their claims that Trump associates potentially colluded with the Russians during the 2016 election.

“This is a pattern we’ve seen from senior-level Trump officials that has gone back months where they deny these contacts or meetings with Russians until proof comes out, then they have to recant,” Ranking Member of the Senate Intelligence Committee, Sen. Mark Warner, D-Va., told Fox News on Tuesday.

“These emails show there is no longer a question of whether this campaign sought to collude with a hostile foreign power to subvert America’s democracy,” Sen. Ron Wyden, D-Ore., said.

But Senate Majority Leader Mitch McConnell, R-Ky., told Fox News on Capitol Hill Tuesday that the Senate Intelligence Committee would look into the matter.

“I'm sure that Senator Warner and Burr will take a look at it,” McConnell said. “They'll get to the bottom of what happened.”

Fox News' Serafin Gomez, Kara Rowland and Chad Pergram contributed to this report.