CAIRO — New divisions in the Muslim Brotherhood appeared on Wednesday as a senior leader hinted that it might walk away from a deal struck with Egypt’s interim military rulers, reflecting signs of confusion and hesitation as the Brotherhood’s most viable bid for power in eight decades has become tangled in the uncertainty and anger gripping Egypt’s streets.

A day after the Brotherhood agreed to the deal with the military that would speed the transition to civilian rule while also enhancing the group’s own political prospects, the senior official said that the security forces had not fulfilled their promise to halt their attacks on protesters in Tahrir Square.

“The killing didn’t stop,” the official, Mohamed Beltagy, general secretary of the Brotherhood’s Freedom and Justice Party, said in a statement on the group’s Web site. “Will our slogan be, ‘No negotiation until after a cease-fire’?”

His warnings came as an increasingly violent uprising has left the group torn between preserving its credibility with protesters and securing the political advantages of cooperating with the ruling military council. Amid the confusion, the Brotherhood’s leaders issued a series of seemingly contradictory statements, culminating Wednesday with several defending the deal from the sharp criticisms of its members and liberals.