Sen. Lindsey Graham, R-S.C., said Tuesday that outgoing United Nations Ambassador Nikki Haley will be a "key player" in the future of American politics.

After Haley appeared with President Trump to announce that she had offered her resignation and would be leaving office by the end of the year, Graham heaped praise on the former governor of his home state of South Carolina and predicted she has a "very bright future."

[READ: Nikki Haley's letter of resignation]

“Ambassador Haley has done an outstanding job as United States Ambassador to the United Nations and showed a level of effectiveness rarely seen by someone in this position," Graham said in a statement. “She is a clear, concise voice for American leadership, American values, and has been a true agent of reform when it came to the United Nations.

“I know all South Carolinians are proud of the service she rendered to our nation and the Trump Administration," he added. “Nikki Haley has a very bright future and will be a key player in both the future of the Republican Party and our nation as a whole for years to come.”

Haley's future in politics is unclear. During her meeting with Trump, Haley said she wanted a break after nearly two years in the Trump administration. She also dismissed speculation that she would run for president in 2020, but did suggest she would hit the campaign trail again to boost Trump for re-election.

"For all of you that are going to ask about 2020, no, I am not running for 2020. I can promise you what I'll be doing is campaigning for this one," Haley told reporters gathered in the Oval Office. "I look forward to supporting the president in the next election."

As Haley heads for the exit, Graham tamped down speculation surrounding himself, reiterating to the media that he has "zero" interest in joining Trump's Cabinet.

"I can do a lot in the Senate. I have zero desire to be a Cabinet member. Kavanaugh one day, Saudi Arabia the next, prison reform the next," he said on the phone, according to the Washington Post's Ashley Parker.