(AP) — The U.S. president is facing perhaps the most daunting question of the war with Iran, one that could define his time in office: Will he send U.S. troops to secure some 970 pounds of enriched uranium that Tehran could potentially use to build nuclear weapons?

Trump has offered shifting reasons for joining Israel in launching the war, but he’s consistently said Iran must “never have a nuclear weapon.”

Much of Iran’s near-bomb-grade nuclear material is believed to be buried under the rubble of a mountain facility pummeled in U.S. bombings Trump ordered last June.

Seizing or destroying it would be risky and complicated, and many nuclear experts say it can’t be done without a sizable, dangerous and politically fraught troop deployment by the Republican leader who has vowed not to entangle the U.S. in another extended and bloody Middle East conflict.