Barry Sadler, who recorded the "Ballad of the Green Berets," was training Nicaraguan rebels in Guatemala and had eceived death threats before he was shot in the head, a friend said.

Sadler, 46, was unconscious and listed in critical but stable condition Tuesday after seven hours of surgery at Veterans Administration Medical Center in Nashville, Tenn., where he was admitted Monday night after being flown from Guatemala City.Physicians were reserving judgment on the possibility of recovery, hospital spokeswoman Patty Zwald said.

"Basically, the doctors have said time will tell," she said.

Duke Faglier, who had lived off-and-on with Sadler in Guatemala for two years, said Sadler had received death threats in the Central American country in recent months.

Sadler, as Staff Sgt. Barry Sadler, co-wrote and recorded "Ballad of the Green Berets" which was the No. 1 song in the country for five weeks in 1966. The song, a tribute to the Special Forces, sold 9 million singles and albums. Billboard Magazine, a weekly trade publication of the music business, named it the No. 1 single of the year.

Sadler had written the song while recuperating from a leg wound suffered in a booby trap in Vietnam, where he served periodically from 1965 to 1967.