Syria is also important to the Shiite-dominated Iraqi government, led by Mr. Maliki. Fearing that Mr. Assad’s overthrow would lead to Sunni control and embolden the Iraqi Sunnis who oppose him, Mr. Maliki has been seen as tolerating the Iranian flights.
American officials have repeatedly insisted that the Iraqis demand that the Iranian flights must land so that they can be inspected. But the Iraqis have only carried out two inspections since July, the State Department official said. One was of an Iranian flight that was on its way back to Tehran after delivering its cargo in Syria. Iran has said the flights are merely carrying humanitarian aid.
Iraq has yet to develop an air force, and since the United States military left the country in 2011, American warplanes no longer patrol Iraq’s skies.
The Iranian flights pose a major challenge for American strategy on Syria. Mr. Kerry has repeatedly said that Obama administration officials want to change Mr. Assad’s calculation that he can prevail militarily, and they want to persuade him to relinquish power and agree to a political transition. But Robert Ford, the senior State Department official on Syria policy, told Congress last week that Iranian and Russian military assistance has fortified Mr. Assad’s belief that his military can still win.