WASHINGTON — The United Arab Emirates, a crucial Arab ally in the American-led coalition against the Islamic State, suspended airstrikes against the Sunni extremist group in December, citing fears for its pilots’ safety after a Jordanian pilot was captured and who the extremists said had been burned to death, United States officials said Tuesday.

The United Arab Emirates are demanding that the Pentagon improve its search-and-rescue efforts, including the use of V-22 Osprey tilt-rotor aircraft, in northern Iraq, closer to the battleground, instead of basing the missions in Kuwait, administration officials said. The country’s pilots will not rejoin the fight until the Ospreys, which take off and land like helicopters but fly like planes, are put in place in northern Iraq.

The United Arab Emirates notified the United States Central Command that they were suspending flights, administration officials said, after First Lt. Moaz al-Kasasbeh of the Jordanian Air Force was captured when his plane went down near Raqqa, Syria. A senior American military official said Islamic State militants “grabbed” Lieutenant Kasasbeh “within just a few minutes.” He added, “There was no time for us to engage.”

But United Arab Emirates officials questioned the American military about whether rescue teams would have been able to reach Lieutenant Kasasbeh even if there had been more time to do so, administration officials said.