(CNN) -- "No negotiating with terrorists" versus "Leave no soldier behind." With the long war in Afghanistan winding down, the plight of Army Sgt. Bowe Bergdahl has left the U.S. government trying to reconcile those two longstanding credos in a bid to win the freedom of the only American solider held as a captive. Bergdahl has been held by insurgents in Pakistan since 2009. Extremely sensitive discussions are under way with intermediaries overseas to see if there is any ability to gain his release, a U.S. official told CNN on Tuesday. The official declined to be identified due to the nature of the discussions, which are being led by U.S. diplomats, although the Defense Department is also involved. Pentagon spokesman Rear Adm. John Kirby declined comment, but Bergdahl's family welcomed the news in a statement on Tuesday.
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NEW: Bergdahl's release is "the highest priority that I have," home-state senator says
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Bowe Bergdahl is the lone U.S. soldier held in captivity
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The U.S. government has launched a new effort to bring him home
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"The clock is ticking" on efforts to bring him home, CNN analyst says
But driving the current effort, according to the U.S. official, is @placeholder's poor health and concern a full troop withdrawal from Afghanistan at year's end would essentially close the door an any rescue attempt.