(CNN) Republican Sen. John McCain is running for reelection in 2016, vying for a sixth term in the Senate.

"I have decided to run for reelection," McCain told NBC News in an interview Monday.

McCain will announce his plans to run for reelection Tuesday at an event in his state of Arizona, a Republican operative briefed on the plan told CNN.

The 78-year-old senator, who will be 80 by Election Day 2016, downplayed concerns about his age, assuring voters that he still has the energy and the fight to be an effective senator.

"I say watch me. Take a look. Take a look at my 18-hour days. Take a look at the hearings we have. Take a look at my legislative accomplishments. Listen, I'm just getting started," McCain said in the interview. "I think I have the knowledge and the background to help this nation through very perilous times and I believe I can still contribute in the many ways to the welfare and benefit of my state."

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