Secretary of State John Kerry, speaking from Paris, declined to say which states had offered to contribute air power, an announcement that White House officials said could await his return to testify in Congress early this week. State Department officials, who asked not to be identified under the agency’s protocol for briefing reporters, said Arab nations could participate in an air campaign against ISIS in other ways without dropping bombs, such as by flying arms to Iraqi or Kurdish forces, conducting reconnaissance flights or providing logistical support and refueling.

“I don’t want to leave you with the impression that these Arab members haven’t offered to do airstrikes, because several of them have,” one State Department official said. “The Iraqis would have to be a major participant in that decision,” the official added. “It has to be well structured and organized.”

The United Arab Emirates, which provided some air power in the 2011 attacks on Libya, seemed at the top of the list, with Qatar hosting an American military headquarters. American officials cautioned that all strikes would have to be approved by the newly assembled government in Iraq, as well as by American military planners. That could prove just one challenge to the offer by Arab nations to participate in airstrikes: While Iraq’s struggling military forces have experience operating with the United States, its Shiite-dominated government has never worked with the Sunni states of the Persian Gulf.

The United States has identified ISIS targets in Iraq over the past several weeks. But officials said they were waiting, in part, to match the allied commitments with actual contributions: warplanes, support aircraft that can refuel or provide intelligence, more basing agreements to carry out strikes, and the insertion of trainers from other Western countries.

Tellingly, there are no plans, as of now, to increase the number of American attack planes in the region. The aircraft carrier Carl Vinson is scheduled to relieve the carrier George H. W. Bush in the Persian Gulf next month; if the Pentagon changed its plans and kept two carriers in the gulf, it could double carrier-based firepower over Iraq and Syria. But for now, there is no plan to do so, officials said. Nor are there any plans to increase American ground-based strike aircraft at facilities around the region, in hopes that Persian Gulf and European allies would make up the difference.

Another striking feature of the American plan, officials said, was the deliberate exclusion of coordination with two other players with an interest — and some ability — to take on ISIS: the government of Iran and the forces of President Bashar al-Assad of Syria, who Mr. Obama declared three years ago was a brutal dictator who had to leave office.