Iran's nuclear program may get more difficult to monitor if no deal is reached with the United States. The U.N. nuclear watchdog has withdrawn its inspectors and nuclear experts believe Iran relocated more than 400 kilograms of highly enriched uranium—enough for 10 nuclear weapons—to a secret location.

Iran's foreign minister says the country is open to resuming nuclear talks with the U.S. if guaranteed no further attacks.

The United States and Iran are poised to return to the negotiating table at a moment when tensions between the two are high and trust is low.