The statement came hours before Saleh was scheduled to sign the agreement and was the latest in a series of mixed signals from Yemen's embattled president.
Saleh backed away from signing at least twice before, adding to the opposition's deep mistrust of a leader known for adept political maneuvering that has kept him in power for decades.
The U.S.-supported deal, mediated by the six-nation Gulf Cooperation Council, calls for Saleh to step down in 30 days and transfer power to his vice president. It also would give him immunity from prosecution.
In the presence of U.S. and EU ambassadors, Yemen's opposition coalition signed the deal Saturday, based on what it said were guarantees that the president would sign on Sunday.
Even if Saleh goes ahead with the planned signing, it is far from certain whether that would satisfy all the many different groups protesting his rule in the streets.
Hundreds of thousands of Yemenis poured into a central square Sunday that has become the center of opposition protests, waving Yemeni flags in rejection of the deal. They held banners that read: "Now now Ali, down with the president," and "Go out Ali."
Women mingled with men, unlike in previous protests when female protesters stood on the edge of the square segregated from men, in keeping with Sharia law that mandates separation of the sexes.
Children had their faces painted with Yemeni flags, while youths carried pictures of slain protesters. Young men and women held a 6-foot-long (2-meter) Yemeni flag.
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.
"This initiative is only meant to save Ali not Yemen. We are going to continue our revolution until the end. Like Tunisia and Egypt, we will go against the opposition if they form a government while Saleh is still in power," declared Tawakul Karman, a protest leader and senior member of the opposition Islamic fundamentalist Islah Party.
She said the protesters were escalating their push by calling a nationwide general strike.
On Saturday, Saleh condemned the proposal as "a coup" and warned the U.S. and Europe that his departure would open the door for al-Qaida to seize control of the fragile nation on the edge of Arabia. Still, an official statement said he would sign it Sunday.
"We accept the initiative to stop bloodshed," Saleh said in a televised speech.
Saleh has managed to cling to power in the face of near daily protests by Yemenis fed up with corruption and poverty. Like other anti-government movements sweeping the Arab world, they took inspiration from the popular uprisings in Tunisia and Egypt.
The president has swung between offering concessions, taking them back and executing a violent crackdown that has killed more than 150 people, according to the opposition, which says it compiled the tally from lists of the dead at hospitals around the nation.
The bloodshed triggered a wave of defections by ruling party members, lawmakers, Cabinet ministers and senior diplomats. Saleh's own tribe has joined those demanding his ouster. Several top army commanders, including a longtime confidant who heads a powerful armored division, joined the opposition and deployed their tanks in the streets of Sanaa to protect the protesters.
Saleh has been able to survive thanks to the loyalty of Yemen's most highly trained and best-equipped military units, which are led by close family members.
That has raised concerns the political crisis could turn into an armed clash between the rival military forces if a deal is further delayed.
Seeking to win some support in the West for his continued rule, Saleh has warned several times that without him, al-Qaida would take control of the country.
"To the Americans and Europeans, al-Qaida is coming and it will take control," he said Saturday in his televised address to members of the security forces. "The future will be worse than the present."
The United States, which had supported Saleh with financial aid and military equipment to fight the country's dangerous al-Qaida branch, has backed away from the embattled leader.
Secretary of State Hillary Rodham Clinton said Saturday Yemenis have been suppressed throughout the country and innocent civilians have died. "President Saleh needs to follow through on his commitment to transfer power," she said in a statement. "The government of Yemen must address the legitimate will of the people."
Al-Qaida in the Arabian Peninsula has an estimated 300 fighters in Yemen and has been behind several nearly successful attacks on U.S. targets, including one in which they got a would-be suicide bomber on board a Detroit-bound flight in December 2009. The explosive device, sewn into his underwear, failed to detonate properly.
The proposal _ first put forward in March by Saudi Arabia, Qatar, Kuwait, Oman, Bahrain and the United Arab Emirates _ gives a clear timetable for a transfer of power.
One week after Saleh signs, the opposition takes leadership of a national unity government that will include representatives of Saleh's party. Parliament will then pass a law granting him legal immunity and a day later _ 30 days after the deal is signed _ he is to step down and transfer power to his deputy.
A month after that, presidential elections are to be held.
