Cancer isn't keeping Sen. John McCain, R-Ariz., from sticking to his political guns.

Just hours after news broke of McCain's brain cancer diagnosis, the Arizona senator blasted President Trump amid a report that the administration decided to halt a CIA training program for moderate Syrian rebels fighting Bashar al-Assad's regime.

"If these reports are true, the administration is playing right into the hands of Vladimir Putin," McCain said in a statement Thursday. "Making any concession to Russia, absent a broader strategy for Syria, is irresponsible and short-sighted."

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The program began under the Obama administration in 2013, and Trump decided to end it about a month ago, The Washington Post reported.

McCain also criticized Trump for not having a broader strategy in Syria and the Middle East in general. "There is still no new strategy for victory in Afghanistan either. It is now mid-July, when the administration promised to deliver that strategy to Congress, and we are still waiting," he added.

McCain announced Wednesday night that he had been diagnosed with a brain tumor after a minor surgery to removed a blood clot above his left eye revealed the glioblastoma.

On Thursday morning, McCain vowed to return to Congress soon. "I greatly appreciate the outpouring of support," he said in a tweet.

Follow Ryan Miller on Twitter @RyanW_Miller