The United States and its allies are straining to maintain Arab support for the war in Libya as pledges of military participation by outside Arab countries have not materialized and popular opinion in the region begins to shift.

On Wednesday, Defense Secretary Robert M. Gates arrived in Cairo to reassure Egyptian officials that the fighting and instability in Libya would not spill over the border, U.S. officials said. Gates met with Egypt’s new prime minister, Essam Sharaf, and was scheduled to see the country’s military ruler, Field Marshal Mohammed Hussein Tantawi, on Thursday.

“The Egyptians obviously have a lot of concerns about Libya,” said a senior U.S. defense official, speaking on the condition of anonymity to discuss the closed-door talks. “I’m sure the field marshal will be anxious to hear from the secretary on what’s going on.”

The Obama administration has said Arab backing was a critical factor in its decision to push for the U.N. Security Council resolution authorizing the military intervention in Libya. Specifically, the White House has cited the Arab League’s endorsement of a no-fly zone over Libya, as well as promises by Arab countries to join in the operation.

Since the no-fly zone was imposed, however, the Arab League has expressed concern about civilian casualties, and no Arab country has yet played a direct military role.

Qatar has deployed four fighter jets to the Mediterranean region and could help enforce the no-fly zone in the coming days, according to NATO officials, but the Persian Gulf emirate has been coy about its precise intentions.

The United Arab Emirates, Jordan and Saudi Arabia — all previously floated as potential Arab partners in the coalition — have either remained silent or rejected entreaties to dispatch armed forces to Libya. Egypt has also demurred, saying it is preoccupied by the revolution that toppled former president Hosni Mubarak last month, according to U.S. officials.

Gates referred indirectly to Qatar’s role Wednesday but gave no indication that other Arab countries would provide air power.

“At least one country is participating, but I don’t know if they’ve announced it yet, so I’m hesitant to do so myself,” he said in response to a reporter’s query about Arab members of the military coalition. “A number are providing support and assistance, for example, overflight rights and access and so on.”

Meanwhile, signs were emerging that Arab public opinion has shifted, with concern growing that the U.S.-led military campaign could turn into a long-term occupation similar to the war in Iraq.

In a carefully worded statement Tuesday evening, Al-Azhar University, Egypt’s preeminent seat of Islamic learning, warned against any foreign occupation of Libyan land and cautioned “the United States of America and European countries against dividing Libya and destroying its human and national wealth, as happened in Iraq.”

The university’s Islamic scholars also criticized Arab leaders — in an implicit reference to the Arab League — for inviting outside intervention in Libya and supporting the no-fly zone.

“We had believed the era of such interventions had gone, never to return,” the statement read. “Al-Azhar condemns the Arab and Islamic world and its institutions and organizations for their negativity and not living up to their duty to resolve our internal political, economic and other problems, which has set the stage for foreign military intervention.”

At a news conference in Cairo, an Egyptian journalist echoed the sentiment by telling Gates of “fears” that Libya could turn into another Iraq and asking how he could guarantee that the United States would not occupy the country.

Gates responded that there were “dramatic differences” between the two military conflicts and emphasized that the White House has pledged not to send ground troops to Libya. He also referred to the Arab League decision to request intervention. “It came from the region itself asking that the United Nations take action to prevent Gaddafi from killing his own people,” he said of Libya’s leader.

Ironically, Gates has been a leading skeptic of the no-fly zone within the Obama administration. Before the U.N. Security Council vote, he warned publicly that Washington should gird for a popular backlash among Arabs if it became involved in a war in another Muslim country.

Signs have also emerged that al-Qaeda’s leadership, which has been noticeably absent from the political unrest across the Arab world, is seeking to exploit public concerns about the U.S. military presence in Libya.

The leader of al-Qaeda’s franchise in North Africa, Abdelmalek Droukdel, warned the Libyan rebel movement this week against trusting the United States and its European allies. Although the air campaign may seem welcome now, he said, the real aim of Western intervention was to get at Libya’s oil riches.

Droukdel hailed “the winds of change” that he said are blowing across the Arab world and urged rebel movements in Tunisa, Egypt and elsewhere to come to the defense of their Libyan counterparts against Moammar Gaddafi.