The defection Monday of Syrian Prime Minister Riad Hijab and his announcement that he was joining the rebel forces was a major coup for the anti-government movement fighting to oust President Bashar al-Assad, U.S. officials and analysts said.

Hijab, who fled to Jordan with his family and several other Syrian officials, said that he was leaving Assad’s “killing and terrorist regime” for “the ranks of the freedom and dignity revolution.” He planned his defection for more than two months with the help of the Free Syrian Army, an opposition force made up of Syrian military defectors and civilian rebels.