Armed supporters of Ali Abdullah Saleh have surrounded an embassy hosting ambassadors from Gulf and western nations, in protest over the scheduled signing of a deal to force the Yemeni leader out of office.
A diplomat told the AFP news agency on Sunday that gunmen had surrounded the Emirati embassy where the head of the GCC, Abdullatif al-Zayani, and ambassadors from Britain, the EU and the US were gathered.
"Everybody is worried. We can't leave the embassy," a Saudi diplomat told the Associated Press.
Saleh was expected to sign the deal, brokered by the Gulf Co-operation Council (GCC), later on Sunday after opposition leaders signed on Saturday.
But Saleh's party said earlier that he would not sign a proposed deal to hand over power "behind closed doors", and instead wanted a public event held for all to attend, including opposition leaders.
The statement, issued by the ruling General People's Congress (GPC) early on Sunday, is the latest in a series of mixed signals from Yemen's embattled president.
Saleh has backed away from signing the deal at least twice before, adding to the opposition's deep mistrust of a leader known for adept political manoeuvring that has kept him in power for decades.
The deal calls for Saleh to step down in 30 days in exchange for legal immunity from prosecution.
Saleh's party insisted that a public ceremony must be held at the presidential palace, and that all political parties, the GCC secretary general, and foreign ambassadors must attend.
Yemen's opposition coalition signed the deal on Saturday, based on what it said were guarantees that the president would sign on Sunday.
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Jamila Ali Rajaa, a former adviser to the Yemeni foreign minister, told Al Jazeera on Saturday that she was optimistic the president would sign the deal.
"I think this time definitely he will," she said.
"There is a lot of pressure on him from the GCC, especially Saudi Arabia, and also from America and the European Union."
But she said the signing of the pact may not end the protests as demonstrators were not willing to leave the places they were occupying, insisting the opposition did not represent them.
Hundreds of thousands poured into a central square that has become the center of opposition protests, waving Yemeni flags and shouting rejection of the deal.
They held banners that read: "Now, now Ali, down with the president!" and "Go out Ali!"
The protesters say the deal falls short of their demands for Saleh's immediate departure and the dismantling of his regime. They also reject any immunity for the Yemeni leader and say the opposition parties don't speak for their demands.
Saleh said on Saturday that al-Qaeda could take over in many parts of the Arabian Peninsula country if he was forced out of office.
"If the system falls ... al-Qaeda will capture Maarib, Hadramout, Shabwa, Abyan and al-Jouf [and] it will control the situation," Saleh said at a ceremony, listing provinces where al-Qaeda's Yemen-based wing has been active.
"This is the message that I send to our friends and brothers in the United States and the European Union ... the successor will be worse than what we have currently.
"We welcome the Gulf initiative and we say that we will work with it in a positive way for the sake of our homeland, (although) in reality it is a mere coup operation ... and part of foreign pressures and agendas."
Saleh has survived many tussles with rivals, and skillfully used patronage and favours to keep tribal and political backers loyal.
But some of his allies, including senior army officers, have abandoned him and joined the opposition as his 32-year rule appears to be entering its final days.
Yemen has been reeling from months of street protests that have seen tens of thousands of people massing in Sanaa, the focal point of demonstrations. Taiz and the port city of Aden have also been scenes of mass protests.