What will Iran do?

At least initially, Iran could try to isolate the United States by working with the other signatories to the deal to preserve the agreement. But Iranian President Hassan Rouhani is under political pressure to show the economic benefits of the deal, which has been questioned all along by his harder-line rivals in the regime. The country’s economy remains sluggish, and a wave of foreign investment has yet to materialize, partly because Western firms have anticipated Trump shredding the deal.

If European investors flee, Iran may conclude there is no longer any benefit to remaining in the deal. The regime could then decide to start breaching the limits imposed on its uranium enrichment and other nuclear work — effectively reviving its program.

The most drastic option would see Iran pull out of the Nuclear Non-Proliferation Treaty and kick out international inspectors, which Western intelligence agencies say have provided a crucial window into and check on Tehran’s nuclear work. This would signal Iran’s intent to build nuclear weapons and permit the regime to pursue weapons-grade enrichment of uranium without United Nations monitors on hand. Estimates vary, but Iran could build a bomb in about a year’s time or less, based on its current stockpiles of uranium.