Strong demand from Gulf countries for Lockheed Martin Corp’s F-35 fighter jet has prompted Washington to grapple with the thorny question about releasing the jet to the region sooner than expected, a senior U.S. defense official said.

Washington has already approved sales of the new stealth fighter to a range of allies, including Turkey, South Korea, Japan and Israel, but sales to the Gulf require a deeper review given U.S. policy guidelines that call for Israel to maintain a qualitative military edge in the Middle East.

Talk about selling the plane to the United Arab Emirates and other U.S. allies in the Gulf came into the open during the Dubai air show last month, with potential buyers weighing whether to buy existing planes or wait for the U.S. government to release the new radar-evading F-35.