Outgoing White House Chief of Staff Ron Klain praised progressive Democrats, insisting that their "leadership has been invaluable to the success" of President Biden's administration the last two years.

"I am so grateful for these kind (too kind) words from ⁦[Rep. Pramila Jayapal, D-Wash.] and @USProgressives," Klain wrote on Twitter in response to parting remarks from Jayapal, who serves as chair of the Congressional Progressive Caucus. "Their leadership has been invaluable to the success of the Biden-Harris administration — and our progress as a country!"

Klain, who has served as head of the Executive Office since Biden took office in January 2021, is slated to depart from his role at the White House following the State of the Union address next month. Biden has named former COVID-19 czar Jeff Zients, a wealthy former health care executive, as Klain's successor in the White House.

Referring to him as a "national treasure," Jayapal said in a statement regarding the transition that Klain "helped ensure that a strong progressive voice was always at the table" and was "a relentless and effective champion of the President’s agenda, helping to shepherd through a raft of the most progressive legislation passed in recent history."

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Pramila Jayapal

Congressional Progressive Caucus Chair Rep. Pramila Jayapal, D-Wash. (Tom Williams/CQ-Roll Call, Inc via Getty Images)

"Every time we celebrate a legislative accomplishment of the last two years, we are celebrating Ron’s tremendous leadership," Jayapal said. "We’ve seen powerful, progressive governance from the Biden Administration and Ron was critical to making so much of that happen. Under the President’s leadership and Ron’s guiding hand, Democrats delivered over and over again for the American people, reminding people that government is the great equalizer of opportunity."

"Squad" Rep. Alexandria Ocasio Cortez, D-N.Y., offered similar praise for Klain late last year, insisting that he is usually a part of "conversations that build trust."

"A lot of people see him as one of the few avenues they have to have a glimpse into the dynamics and considerations of what’s happening in the White House," Ocasio Cortez said of Klain. "When I think about some of the conversations that build trust, build the sense of open communication, he’s usually part of that."

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Ron Klain

White House Chief of Staff Ron Klain is slated to depart from his role following Biden's State of the Union address next month. (Andrew Harrer/Bloomberg via Getty Images)

Biden, who announced officially Friday that Zients would serve as his next chief of staff, also offered solemn remarks in a statement about Klain.

"I’ve known Ron Klain since he was a third-year law student," Biden said. "He came to work for me on the Senate Judiciary Committee, and I knew the moment he started that he was a once-in-a-generation talent with a fierce and brilliant intellect. Just as important, he has a really big heart."

Noting that the two of them had been "through some real battles together," Biden said Klain "knows how government works, how politics works, how Congress and the White House works."

"He is as tough, smart, determined, and persistent as anyone I have ever met," Biden added of Klain. "He assembled the most diverse and the most talented White House team in history and leaned on them to solve impossible challenges."

Ron Klain, Joe Biden

President Biden, left, and Chief of Staff Ron Klain meet with cabinet members and immigration advisors in the State Dining Room on March 24, 2021 in Washington, DC. (Chip Somodevilla/Getty Images)

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Although his departure will come well ahead of the 2024 presidential election, Klain made it clear this week that he would support Biden should he decide to seek a second term in the White House.

During a Friday appearance on MSNBC, Klain said he would do whatever he could to be "helpful to get [Biden] elected" in 2024.