SANAA, Yemen -- The signing ceremony for a deal to end Yemen's political crisis was postponed indefinitely Sunday after the Yemeni president refused to sign it personally, a Gulf official said, signaling the possible collapse of the agreement.
Ahmed Khalifa al-Kaabi, a media official for the six Gulf Arab nations sponsoring the agreement, told The Associated Press that their foreign ministers would meet in the Saudi capital, Riyadh, on Sunday to try to find a way to salvage a deal.
The standoff between Yemeni President Ali Abdullah Saleh and the hundreds of thousands of street protesters demanding his immediate departure after 32 years in office threatens to pull the impoverished and fragile nation into greater disorder and destabilize the rest of the Arabian peninsula.
The Gulf Cooperation Council, an association of Yemen's oil-rich neighbors, offered a deal that calls for Saleh to step down within 30 days and for the ruling party and the opposition to come together in a national unity government. In exchange, Saleh would get immunity from prosecution.
The GCC comprises Saudi Arabia, Kuwait, United Arab Emirates, Qatar, Oman and Bahrain.
Yemen's opposition parties, which had initially agreed to the deal, said they would not sign it if Saleh refused to do so personally.
For their part, representatives of the those staging anti-Saleh demonstrations since early February have rejected the deal outright, demanding that Saleh immediately step down and face trial for the killings of protesters and corruption.
They say the established opposition political parties taking part in the talks do not represent them, and even if a deal were reached it seemed unlikely that it would end the protests.
The ceremony was expected to be held in Riyadh on Sunday or Monday.
In what appeared to be a last-minute bid to salvage the deal, Saudi Arabia's King Abdullah spoke to Saleh by telephone on Sunday, according to a brief Yemeni government statement.
The deal's collapse would raise the prospects of more bloodshed in a nation already beset by serious conflict and deep poverty and which is home to al-Qaida's most active offshoot.
At least 140 people have died in the government's crackdown on the protests, which have nonetheless grown in number week after week. The violence has prompted several top military commanders, ruling party members, diplomats and others to defect to the opposition.
Still, Saleh has clung to power and has the key backing of Yemen's best trained military units, which he placed under the command of one of his sons and other close relatives.
Al-Kaabi's citing of Saleh's refusal to personally sign the deal indicated the GCC blamed him for the deadlock.
Government officials said Saleh had told GCC Secretary-General Abdullatif bin Rashid al-Zayani on Saturday that he intended to ratify the deal after sending a close aide and a senior ruling party official to sign it.
The officials spoke on condition of anonymity because they were not authorized to speak to the media.
The opposition, whose leaders have said before that they have little trust in Saleh's word, feared he was leaving himself room to stay in power.
Leaders of the street demonstrations said they planned to step up their protests to force Saleh out.
Tens of thousands of protesters were out Sunday in a number of Yemeni cities, including Aden and Taiz in the south, to demand that he step down.
"We will not pay attention to any mediation or foreign intervention," said protest leader Abdel-Hadi al-Azazi in Sanaa, the capital. "We will continue to march and protest until the uprising's goal is achieved -- the ouster of the regime."