CAIRO — An Arab League committee has given Syria 24 hours to agree to allow an observer mission into the country or it could face sanctions.

Thursday’s threat comes as international pressure mounts on President Bashar Assad to stop the brutal crackdown on an uprising against his regime. The U.N. says 3,500 people have been killed in the crackdown since March.

The Cairo-based Arab League called on Damascus to agree to an observer mission by Friday. If they refuse, the League will meet Saturday to decide on sanctions that could include stopping flights to Syria, ending financial dealings with Damascus and freezing Syrian assets.