Updated

A Gulf official says the six-nation Gulf Cooperation Council mediating Yemen's power transfer will drop the U.S.-backed deal and withdraw from mediation if Yemeni President Ali Abdullah Saleh doesn't sign it by the end of the day.

The warning came as a mob of armed Saleh loyalists encircled the United Arab Emirates Embassy trapping the U.S., British, Saudi and European ambassadors inside. Saleh was to have signed the deal Sunday.

The pact gives Saleh immunity of prosecution if he steps down within 30 days. He has faced near daily protests for an end to his 32-year rule.