WASHINGTON (Reuters) - The head of European planemaker Airbus said novel open-rotor technology being tested by engine maker CFM International offers promising efficiencies and reductions in emissions but that the "jury is out" on whether it will be viable.

Chief Executive Guillaume Faury also told reporters on the sidelines of the Global Aerospace Summit, hosted by the U.S. Chamber of Commerce, that deliveries of the current generation of LEAP engines built by CFM International continue to be late.

"They are late in their deliveries," he said.