America’s large defence groups have for decades relied on international allies to boost the sales of many of their weapons. However, the Trump administration’s wavering commitment towards the Nato alliance has prompted several countries to question their reliance on US armaments — triggering growing alarm among some industry executives.

“I am concerned that pure politics could damage our prospects in future competitions,” said one executive at a leading US contractor.

The concerns have put the spotlight on the F-35 fighter, America’s most expensive defence programme and the biggest single revenue generator for defence group Lockheed Martin. Although the stealth fighter is the backbone of modern western air forces, some are worried as to whether the US could immobilise weapon systems with a so-called “kill switch”.