A dancer with the Moscow Ballet who disappeared before his troupe's final appearance in Dallas on Friday, has asked for political asylum, a State Department official told the Fort Worth Star-Telegram. "We're very aware of the situation," the spokesman told the paper. Meanwhile, the Dallas Times Herald quoted Oliver Revell, the FBI's executive assistant director, as saying that the dancer, Andrei Ustinov, who is in his 30s, had sought permission to defect. But FBI spokesman Bob Moran said later that Revell was not aware of the Ustinov case when contacted by the paper and thought he was answering hypothetical questions concerning defections. Ustinov, who has a wife and child in the Soviet Union, joined the ballet as a principal soloist for its two-month, 21-city American tour.