WASHINGTON (REUTERS) - The US military on Thursday said it had grounded the entire fleet of Lockheed Martin Corp F-35 fighter jets until completion of additional inspections of the warplane's single engine built by Pratt & Whitney, a unit of United Technologies Corp.

The Pentagon's F-35 program office, Air Force and Navy issued directives on Thursday ordering the suspension of all F-35 flights after a June 23 fire on an Air Force F-35A jet at a Florida air base, according to statements by the Pentagon and the F-35 program office.

The Pentagon said US and industry officials had not been able to pinpoint the cause of the fire, which occurred as a pilot was preparing for takeoff. The pilot was not injured.

The Pentagon said preparations were continuing for F-35 jets to participate in two UK air shows later this month, but a final decision would be made early next week.