One option, U.S. and Arab officials said, would be to bring Yemen before the U.N. Security Council for unspecified sanctions. On Monday, the European Union called on Saleh to “transfer power now” and warned that member states “will review their policies toward Yemen.”

But even as they considered new steps to resolve the escalating crisis in Yemen, which is in its third month, officials acknowledged that any course of action they might pursue poses risks in this strategically located country that is on the brink of economic collapse and is home to the world’s most powerful and active branch of al-Qaeda.

“The situation is very delicate now,” said the administration official, who spoke on the condition of anonymity to discuss fast-breaking events on the ground. Saleh, he said, “is drawing this out at his own peril.”

In the Yemeni capital, Sanaa, gun battles raged Monday between government forces and fighters loyal to powerful tribal leader Sadiq al-Ahmar, who has sided with the growing opposition movement that has demanded an end to Saleh’s 32-year-long rule, wire services reported.

The U.S. Embassy in Sanaa announced it would close its consular section Tuesday and Wednesday “due to the fluid security situation” and would provide emergency services only for U.S. citizens.

“We’re taking one day at a time, but we’re not at this point relying on a change of heart on the part of Saleh,” the administration official said. “We need to now reevaluate with our partners the next step we can take that will try to resolve this.”

A senior Arab official, who also spoke on the condition of anonymity, said, “Right now, there is nothing the outside world can do except saying, ‘Sign.’ ”

But while donors may be hesitant about cutting security ties and the economic assistance that keeps Yemen afloat, he said, “you can cut the stuff that goes to him as president — not directly into his pocket, but presidents have expenses. They live in houses, they have cars and salaries to pay.”

The Arab official counseled a bit more patience, but he agreed that time was running out. “It’s going to be impossible for [Yemen] to continue without the risk of this disintegrating. In which case, all bets are off,” he said.

Yemen, an ostensible U.S. ally in the fight against al-Qaeda and other terrorist groups, has been one of the most vexing problems for the Obama administration during a season of widespread popular revolts throughout the Arab world.

Yemen, which received more than $300 million in U.S. security and economic aid last year, allows U.S. Special Operations forces to train its counterterrorism forces and gather intelligence on its soil against al-Qaeda in the Arabian Peninsula (AQAP). U.S. fighter jets have launched attacks on AQAP targets in Yemen, and this month marked the first time since 2002 that the U.S. military launched a drone strike there.

“I don’t believe that AQAP has been anywhere near the forefront of this political movement” comprising youthful protesters and civil society groups, political parties, tribal leaders and breakaway military units, the senior administration official said. “But if the military and the security services fracture, AQAP is going to be the one that benefits.”

The tens of thousands of Yemenis pouring into Sanaa to oppose or support Saleh are seen as providing a useful cover for AQAP to move large quantities of weapons into the capital and, potentially, to plan attacks against Western and other targets there.

The administration has tried to track military units involved in the political fighting on both sides to ensure that U.S.-trained counterterrorism units and U.S.-provided equipment have not been involved in the domestic battles. “So far, there’s not been a bleed-over” from the specially trained units into the streets, the official said.

But as frustration with Saleh has increased along with the violence, the administration has moved from gently advising him to make an early exit to vocally calling for him to step down in accordance with negotiated deals he has repeatedly agreed to but balked at signing.

Yemen’s Persian Gulf neighbors, nervously fending off their own domestic unrest, have taken the lead in negotiations. The most recent deal, negotiated by the Gulf Cooperation Council, a six-nation regional group that includes Saudi Arabia and the United Arab Emirates, came after Yemeni opposition leaders dropped their reluctance to grant Saleh immunity from prosecution if he agreed to step down in 30 days.

Saleh agreed, and the opposition signed the deal Saturday. A signing ceremony for Saleh and leaders of his political party was scheduled to take place Sunday at the UAE Embassy.

Instead, the embassy was surrounded by armed men professing loyalty to Saleh. Diplomats, including the U.S. and Saudi ambassadors and the head of the GCC, were surrounded for several hours before being evacuated, some on helicopters, by government forces.

When they reassembled Sunday afternoon at the presidential palace, Saleh stood chatting amiably with U.S. Ambassador Gerald M. Feierstein as his party leaders signed the agreement, but then he refused to do so himself.

In a later appearance on state television, Saleh said he had refused because opposition leaders had not signed the document in his presence. He said the opposition would be responsible “if the country goes to civil war.”

GCC officials left Yemen in anger, announcing that the deal was off the table and beginning urgent consultations with one another and the Obama administration.