WASHINGTON (AP) — The U.S. military is experiencing a “beyond critical” shortage of advanced missile interceptors in Europe largely driven by President Donald Trump’s war with Iran, a U.S. defense official in Europe and a NATO official told The Associated Press, raising concerns about vulnerabilities in NATO countries to a potential Russian attack.

The U.S. defense official said the most concerning shortfall involves Patriot missile interceptors, which can shoot down Russia’s high-speed ballistic missiles. The NATO official confirmed the low inventories of Patriots among American and NATO forces in Europe. Both spoke on condition of anonymity to discuss sensitive military matters.