Sen. John McCain John Sidney McCainMomentum growing among Republicans for Supreme Court vote before Election Day McConnell urges GOP senators to 'keep your powder dry' on Supreme Court vacancy McSally says current Senate should vote on Trump nominee MORE (R-Ariz.) said in an interview broadcast late Sunday that he feels "more energetic" and motivated as a result of his brain cancer diagnosis.

"I am more energetic and more engaged as a result of this because I know that I’ve got to do everything I can to serve this country while I can," McCain told CBS's "60 Minutes."

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McCain, who is undergoing both radiation and chemotherapy treatments, described his prognosis as "very poor."

"Some say 3 percent, some say 14 percent. You know, it's a very poor prognosis.

The senator also joked that he is fighting the cancer by eating "lousy" tasting food.

"One criteria to feeding people that are under my situation, it has to taste lousy," he said.

In July, doctors discovered McCain had a tumor after he underwent a procedure to remove a blood clot.

"Subsequent tissue pathology revealed that a primary brain tumor known as a glioblastoma was associated with the blood clot," his hospital said in a statement at the time.

The Arizona senator announced on Friday that he will vote against the latest GOP bill to repeal ObamaCare.

McCain was also the key "no" vote that killed another GOP push to repeal and replace ObamaCare earlier this year.