Medvedev over the weekend warned “a number of countries are ready to directly supply Iran with their own nuclear warheads.”

President Donald Trump on Tuesday injected some uncertainty over whether the U.S. would abide by the mutual defense guarantees outlined in the NATO treaty as he headed to its summit — comments that could revive long-standing concern from European allies about his commitment to the military alliance.

Allies are poised to pledge to more than double their defense spending to reach a target the president pushed for earlier this year.