What is the Iran nuclear deal and why does it matter if the U.S. withdraws?

The Iran nuclear deal was the signature foreign policy achievement of former President Barack Obama’s administration.

Over two-and-a-half-years, former Secretary of State John Kerry helped broker the deal, which is officially known as the Joint Comprehensive Plan of Action, or JCPOA.

The European Union, Russia, China, France, Germany, the United Kingdom and the U.S. made the deal with Iran for stricter limits on the nation's nuclear energy and enrichment programs in exchange for lifting the crippling economic sanctions against Tehran.

Iran agreed to accept provisions of the deal in 2015, including limits on uranium-enriching activities for at least eight years, restrictions on its uranium stockpile for 15 years and monitoring of its uranium ore production for 25 years, according to PBS.

International inspectors have confirmed, despite conflicting assertions from Israel, that Iran has not violated the terms of the JCPOA.

Trump is threatening to reimplement economic sanctions against Iran as it pulls out of the deal, something that would put the U.S. in violation of the agreement.

If the Trump administration re-imposes sanctions against Iran, it puts the U.S. in non-compliance with the JCPOA, although Trump can officially withdraw the U.S. from the deal through an executive order, PBS reported.

PBS, citing analysts, reported the U.S. may already be in violation of the agreement on several fronts, including not moving forward on a deal to sell civilian aircraft to Iran.

Iran’s President Hassan Rouhani has indicated the JCPOA could remain intact without the U.S. under certain conditions, but he also threatened to reinstate the country’s nuclear programs if the deal collapses completely.

The European Union has indicated it wants to keep the agreement intact, without the U.S., if necessary, but it's unclear how that might happen.