As demonstrators for and against President Ali Abdullah Saleh mustered for a new round of competing rallies on Friday, the Yemeni leader was engaged in serious negotiations over the timing and conditions for the end of his 32-year rule, Yemeni and American officials said.
But, speaking on Thursday, the officials cautioned that no deal had been reached. In a television appearance, Mr. Saleh, in power for three decades, struck a defiant pose, referring scornfully to antigovernment protesters while offering amnesty to military defectors who return to the government’s side.
Nonetheless, the four-week-old protest movement appeared to be gaining momentum with the defections in the past week of a host of high-level government officials, including senior military commanders and ambassadors, and the protesters’ rejection of Mr. Saleh’s latest offer, to leave office by the end of the year.
The demonstrations on Friday are expected to be among the largest for both the anti- and pro-government sides. The antigovernment protesters have called Friday the “Day of Departure” and will gather after prayers at their usual location near Sana University.
Witnesses reported sharply increased security on the streets of the capital as Mr. Saleh prepared to deliver an open-air address to his supporters, who were arriving by the thousands for Friday prayers and a rally in Tahrir Square. Mini-buses displayed large posters of him on the passenger side of the windshield; men riding in cars’ trunks waved Yemeni flags as they criss-crossed the city. But news reports said security forces had thrown up checkpoint around the city, seeking to prevent anti-Saleh demonstrators from flooding into the capital.
A week earlier, around 100,000 antigovernment protesters gathered for Friday Prayers just before snipers opened fire on the crowd.
A large number of pro-Saleh tribesmen, widely believed to be being paid by the governing party, entered Sana on Wednesday to rally around the president. The official Saba news agency has claimed that two million government supporters will mass in Sana’s main square on Friday morning for what they have called their “Day of Tolerance.”
Mr. Saleh spoke Wednesday night with the country’s most powerful military leader, Maj. Gen. Ali Mohsin al-Ahmar, a longtime ally who abandoned the president this week and directed his troops to protect the demonstrators.
General Ahmar also spoke on television on Thursday and said he had no interest in political power. “Military rule in the Arab world is outdated,” he declared.
Some reports suggested that both men might step down in a matter of days or weeks to make way for a transitional government and the writing of a new constitution. But one senior American official who was following events in Yemen closely said the immense complexity of Yemen’s tribal society, and Mr. Saleh’s history of brinkmanship, argued for caution.
“The general assumption is that his days are numbered,” said the official, who was not authorized to speak on the record. “But he seems determined to decide the number himself.” The official cautioned that the discussions about Mr. Saleh’s exit are “not just talks in a room” but negotiations involving representatives of 20 or more Yemeni factions and interest groups, often through intermediaries.
According to several accounts, the talks are being closely monitored by representatives of Saudi Arabia, Yemen’s wealthy northern neighbor, and the United States Embassy, which has relied on Mr. Saleh as an ally against the Qaeda branch in Yemen.
“We want to express support for a transition and concern about our security issues,” the American official said. “But we don’t want to take sides.”
Another important tribal leader threw his support to the antigovernment movement on Thursday, adding to the pressure on Mr. Saleh.
Sheik Sinan Abu Lahoum, a leader in the important Bakil tribal confederation, announced his position via a telephone call to the antigovernment sit-in. Mr. Abu Lahoum, who is in the United States for health reasons, said “my age and my health does not permit me to participate with the youth” and urged all Yemenis to participate in the revolution for the sake of the country.
The announcement followed that of the influential tribal leader Sheik Sadeq al-Ahmar, who heads the Hashid confederation, the tribal confederation to which the president belongs.
The raft of desertions accelerated after the killing of at least 50 protesters last Friday by government-linked snipers. Analysts said the defections were compelled by the taboo in Yemeni tribal culture against killing innocent, unarmed civilians.
Yassin Saeed Noman, the head of the opposition political coalition, said in an interview that Mr. Saleh “wants a peaceful transfer of power.” But the opposition has rejected Mr. Saleh’s offer to step down at year’s end, and Mr. Noman said no transition should leave the president in power more than “one or two months.”
Mr. Noman, who has been widely discussed as a possible prime minister in an interim government, said the terms of Mr. Saleh’s departure were no longer up to the political opposition. “It depends on people in the streets,” he said.
Meanwhile, there were reports of minor clashes around the country between loyalist military forces and those following General Ahmar. In Jawf, a northern province on Yemen’s border with Saudi Arabia known for being home to both Houthi rebels and Qaeda militants, local reports have said that all government officials have been forced out of the province. A tribal leader said a popular committee was now running all security and administrative duties.
The office of the Arab satellite news station Al Jazeera was closed Wednesday in Sana when the Information Ministry announced it would suspend the channel’s permit, according to Khaled al-Hammadi, a producer for Al Jazeera.
“I think they want to do something important during the upcoming few days,” he said by phone. “For that they want to close all the media.”
On Wednesday morning, the Yemeni government issued a statement urging “foreign media to exercise maximum accuracy as to what they report and to be professional while covering the situation in Yemen.”