American defense firms are following the money. Boeing opened an office in Doha, Qatar, in 2011, and Lockheed Martin set up an office there this year. Lockheed created a division in 2013 devoted solely to foreign military sales, and the company’s chief executive, Marillyn Hewson, has said that Lockheed needs to increase foreign business — with a goal of global arms sales’ becoming 25 percent to 30 percent of its revenue — in part to offset the shrinking of the Pentagon budget after the post-Sept. 11 boom.

American intelligence agencies believe that the proxy wars in the Middle East could last for years, which will make countries in the region even more eager for the F-35 fighter jet, considered to be the jewel of America’s future arsenal of weapons. The plane, the world’s most expensive weapons project, has stealth capabilities and has been marketed heavily to European and Asian allies. It has not yet been peddled to Arab allies because of concerns about preserving Israel’s military edge.

But with the balance of power in the Middle East in flux, several defense analysts said that could change. Russia is a major arms supplier to Iran, and a decision by President Vladimir V. Putin to sell an advanced air defense system to Iran could increase demand for the F-35, which is likely to have the ability to penetrate Russian-made defenses.

“This could be the precipitating event: the emerging Sunni-Shia civil war coupled with the sale of advanced Russian air defense systems to Iran,” Mr. Aboulafia said. “If anything is going to result in F-35 clearance to the gulf states, this is the combination of events.”

At the same time, giving the gulf states the ability to strike Iran at a time of their choosing might be the last thing the United States wants. There are already questions about how judicious Washington’s allies are in using American weaponry.

“A good number of the American arms that have been used in Yemen by the Saudis have been used against civilian populations,” said Daryl Kimball, executive director of the Arms Control Association, an assertion that Saudi Arabia denies.

Mr. Kimball said he viewed the increase in arms sales to the region “with a great deal of trepidation, as it is leading to an escalation in the type and number and sophistication in the weaponry in these countries.”