Iran is set to breach a cap on its enriched-uranium stockpile within days, potentially pushing its conflict with the U.S. into a dangerous new phase.

Limiting the volume and purity of its accumulated uranium was a central part of Iran’s nuclear deal with world powers in 2015. The U.S. abandoned the deal in May 2018 and reimposed sanctions. President Donald Trump said Saturday he’ll impose “major” additional U.S. penalties on Monday.

While Trump announced the sanctions, days after Iran shot down a U.S. Navy drone, he didn’t provide details. In his Twitter post Trump specified the need to prevent Iran from acquiring nuclear weapons, echoing comments made to reporters at the White House on Saturday.

“All I want is no nuclear…