Utah Senator Orrin Hatch, the longest-serving GOP senator, announced Tuesday that he would not seek re-election in 2018 – opening up a possible pathway to the political resurrection of 2012 Republican presidential nominee Mitt Romney.

Hatch, 83, who first took his seat in 1977, had been debating whether to run again, and President Trump had publicly beseeched him not to retire.

In a video statement released Tuesday, however, Hatch said that he would vacate his seat at the end of his term.

"I was an amateur boxer in my youth, and I brought that fighting spirit with me to Washington,” Hatch said. “But every good fighter knows when to hang up the gloves. And for me, that time is soon approaching.”

Romney, a former governor of Massachussets and a vocal critic of the president, is widely reported to be considering running for Hatch’s seat. In a statement, Romney said Hatch had "represented the interests of Utah with distinction and honor."

The move is a blow for Trump, who pushed Hatch to stay on in a visit to Utah in December.

“We hope you will continue to serve your state and your country in the Senate for a very long time to come,” Trump said.

Hatch has been a strong supporter of the president’s agenda, and as chairman of the Senate Finance Committee was a key player in getting the tax reform bill passed in December.

White House Press Secretary Sarah Huckabee Sanders said at the daily press briefing on Tuesday that Trump was "very sad" to see Hatch leave.

“The president certainly has the greatest and deepest amount of respect for Senator Hatch and his over four decades of experience in the Senate,” Sanders said. “He is particularly thankful for the senator's leadership and massive effort that he played and the role that he played in getting the tax cut and reform package passed.”

Trump later took to Twitter to congratulate Hatch "on an absolutely incredible career."

"He has been a tremendous supporter, and I will never forget the (beyond kind) statements he has made about me as President. He is my friend and he will be greatly missed in the U.S. Senate!" the president said.

In his statement, Hatch noted that he had authored more bills that became law than any living member of Congress. He also hailed the passage of the Religious Freedom Restoration Act as one of his proudest legislative achievements.

“I'm deeply grateful for the privilege you've given me to serve as your senator these last four decades,” he said in the statement. “I may be leaving the Senate, but the next chapter in my public service is just beginning.”