The embassy closing and travel warning came as the death toll from this week's clashes between police and demonstrators in Egypt reached topped 600, and supporters of ousted Egyptian President Mohamed Morsi stormed and set fire to the offices of the governor of Giza.
U.S. President Barack Obama announced Washington has canceled next month's joint U.S.-Egyptian military exercise, saying traditional cooperation with Egypt "cannot continue as usual."
Obama chastised the government for the crackdown on protests and extended condolences to the victims' families.
"The United States strongly condemns the steps that have been taken by Egypt's interim government and security forces," he said.
The State Department said routine consular services would be suspended for the day.
"As a matter of general practice, U.S. citizens should avoid areas where large gatherings may occur," the department said. "Even demonstrations or events intended to be peaceful can turn confrontational and possibly escalate into violence. U.S. citizens in Egypt are urged to monitor local news reports and to plan their activities accordingly."