SANAA, Yemen (AP) - Yemen's embattled president agreed Saturday to a proposal by Gulf Arab mediators to step down within 30 days and hand power to his deputy in exchange for immunity from prosecution, a major about-face for the autocratic leader who has ruled for 32 years.

A coalition of seven opposition parties said they also accepted the deal but with reservations. Even if the differences are overcome, those parties do not speak for all of the hundreds of thousands of protesters seeking President Ali Abdullah Saleh's ouster, and signs were already emerging that a deal on those terms would not end confrontations in the streets.

A day earlier, protesters staged the largest of two months of demonstrations, filling a five-lane boulevard across the capital with a sea of hundreds of thousands of people. Day after day of protest have presented a stunning display of defiance in the face of a crackdown that has included sniper attacks and killed more than 130 people.

The uprising and a wave of defections by allies, including several top military commanders, have left Saleh clinging to power and now appear to be pushing him to compromise on his earlier refusal to leave office before his term ends in 2013.

For decades the former military officer has fended off numerous challenges, deftly maneuvering among the nation's powerful and fractious tribes and using security forces to put down opponents. Al-Qaida's most active franchise has attacked his forces, an armed rebellion has battered the north of the country and a secessionist movement has reappeared in the once-independent south.

At the same time, the country is rapidly running out of water and oil and is the poorest in the Arab world.

The United States has watched the uprising with particular concern because Saleh has been an ally in fighting al-Qaida in the Arabian Peninsula, which is based in Yemen's remote mountainous south and has made several nearly successful attempts to attack U.S. and other targets abroad.

U.S. State Department spokesman Mark Toner said Washington welcomes the proposal for ending the crisis and called for immediate dialogue by all sides on a transfer of power.

``We will not speculate about the choices the Yemeni people will make or the results of their political dialogue,'' he said. ``It is ultimately for the people of Yemen to decide how their country is governed.''

Later, the White House in a statement urged all parties in Yemen ``to move swiftly to implement'' a deal transferring power.

The opposition movement, fed up with poverty and corruption under Saleh, took inspiration from the toppling of leaders in Tunisia and Egypt and has grown in numbers since the first protests in early February.

The six-nation Gulf Cooperation Council, which includes powerful Saudi Arabia, has been seeking to broker an end to the crisis in the fragile nation on the southern edge of the Arabian peninsula.

Under the latest draft, Yemen's parliament would grant Saleh legal protection from prosecution. The president would submit his resignation to lawmakers within 30 days and hand power to his vice president, who would call for new presidential elections.

Opposition spokesman Mohammed Kahtan described the Gulf council's initiative as ``positive'' and said the leaders of the opposition parties have all agreed on it.

Kahtan, however, listed several reservations. He said the opposition rejects the draft proposal's call for the formation of a national unity government within seven days of the signing of a deal and wants to see Saleh step down first.

``We would have to swear an oath to Saleh, who has already lost his legitimacy,'' he explained.

They are also against giving Yemen's parliament - dominated by Saleh's party _ the power to approve or reject his resignation, which opens to the door to allowing the president time to stall.

Mohammed al-Sabri, another spokesman of the opposition, said that if the parties sign the initiative it does not mean that the mass protests will come to a quick end.

``We don't represent everybody in the squares. We only represent the political parties,'' he said.

A spokesman for the youth movement that is one of the key organizers of street protests said any deal that protects him from prosecution is unacceptable.

He should be held responsible for the killings of protesters and corruption, said Khaled al-Ansi.

``The youth of the revolution reject any initiative that gives immunity to the president, who collaborated in killings of civilians and in corruption,'' he said. ``The GCC initiative is actually violating the basic principles of justice.''

State TV announced the president's acceptance of the deal and said Yemen's foreign minister delivered the government's response to mediators on Saturday.

The foreign minister of the United Arab Emirates, Sheik Abdullah bin Zayed Al Nahyan, met in the Emirati capital Saturday with his Yemeni counterpart, Abu Bakr al-Qirbi, and urged him to accept the GCC plan, the official UAE news agency WAM reported.

Protests continued throughout the day and expanded to include a general strike.

Schools, government offices and private companies shut their doors in response to the Yemeni opposition's call for a strike aimed at putting more pressure Saleh to step down.

Thousands of protesters kept up sit-ins at city squares in at least five provinces, while Saleh accused the opposition of ``dragging the country into a civil war'' in a televised speech to a military academy.

Saleh has over the past two months used violence to try to quell the unrest. He has also offered concessions, including a pledge not to run again for president when his term is up in 2013 or allow his son to succeed him, but to no avail.