The younger brother of the Soviet-backed leader of Afghanistan has defected to the United States in a move that State Department officials say could tarnish Najibullah's image.

The Afghan ruler and his brother, Saddiqullah Rahi, were said to have been at odds for years. Saddiqullah was under death threat and was protected for months by an anti-government faction that then spirited him out of Afghanistan to Pakistan, said two U.S. officials, who spoke Thursday on condition of anonymity.The two brothers sometimes go by shorter names. Najibullah is also known as Najib, and Saddiqullah as Saddiq.

Saddiqullah, 37, his wife, Soraya, and their two sons reached the United States Wednesday from Frankfurt, West Germany, and have been given sanctuary, the officials said.

"He was accepted in this country as a refugee," an official told The Associated Press. "No special deals were made, but the processing was expedited. Elaborate security precautions have been taken."

Saddiqullah apparently joined the forces of Ahmed Shah Massoud, the rebel field commander who has led the fight against Afghan troops and Soviet forces in Panjshir valley.