President Donald Trump appears increasingly likely to refuse to certify the Iran nuclear agreement later this month, a decision that could place the future of one of the Obama administration's signature foreign-policy achievements in the hands of Congress and deepen tensions between Washington and Tehran.

Trump has repeatedly condemned the 2015 agreement, formally known as the Joint Comprehensive Plan of Action, or JCPOA, calling it one of the worst agreements ever negotiated by the United States.

Now he faces an October 15 deadline to determine whether to certify the agreement under U.S. law.

The decision does not directly determine whether Iran is complying with every technical restriction of the nuclear agreement. Instead, the certification process established by Congress requires the administration to periodically make several determinations about the deal, including whether continued sanctions relief remains appropriate and proportionate to the measures Iran has taken regarding its nuclear program.

Trump has given increasingly strong indications that he is unwilling to make that certification again.

What the Iran Deal Does

The JCPOA was negotiated during President Barack Obama's administration and reached in 2015 between Iran, the United States, Britain, France, Germany, Russia, China and the European Union.

Under the agreement, Iran accepted extensive restrictions on its nuclear activities in exchange for relief from international economic sanctions.

Iran agreed to sharply reduce its stockpile of enriched uranium, limit uranium enrichment to low levels, reduce the number of centrifuges operating at its nuclear facilities and redesign its heavy-water reactor at Arak.

The International Atomic Energy Agency was given extensive authority to monitor Iran's nuclear facilities and verify implementation of the agreement.

Supporters argue that those restrictions make it substantially more difficult for Iran to produce enough nuclear material for a weapon.

Critics, including Trump, argue that some of the restrictions eventually expire and that the agreement fails to adequately address Iran's ballistic missile program, support for militant groups and other activities throughout the Middle East.

Trump Has Never Accepted the Deal

Trump campaigned aggressively against the agreement during the 2016 presidential election.

Since taking office, however, his administration has twice certified Iran's compliance under the congressionally mandated review process.

Trump has made clear that he was reluctant to do so.

During his September address to the United Nations General Assembly, Trump again attacked the agreement, calling it an embarrassment to the United States and signaling that a major change in American policy toward Iran could be approaching.

His administration is conducting a broader review of Iran policy that goes beyond the country's nuclear program.

White House officials have emphasized Iran's ballistic missile development, its support for Hezbollah and other armed groups, and its influence in conflicts across the Middle East.

The administration's argument increasingly appears to be that judging the nuclear agreement solely by Iran's compliance with its technical nuclear provisions is too narrow.

The Certification Question

The distinction between the nuclear agreement itself and the American certification requirement is important.

The October 15 certification is required under the Iran Nuclear Agreement Review Act, a U.S. law passed in 2015.

Refusing certification would not automatically terminate the JCPOA or immediately restore all American sanctions.

Instead, it would give Congress an opportunity to consider whether nuclear-related sanctions that were suspended under the agreement should be reimposed.

That could create an extraordinary situation in which the United States challenges the continued viability of an international nuclear agreement even as the other countries participating in it remain committed to the accord.

European governments have urged Washington to preserve the agreement.

International Inspectors Continue Monitoring Iran

The International Atomic Energy Agency remains responsible for verifying Iran's nuclear commitments under the JCPOA.

That creates another complication for the administration.

Trump's objections extend well beyond the narrow question of whether Iran is observing restrictions on uranium enrichment, centrifuges and nuclear material.

The president and his advisers argue that Iran's broader behavior must also be considered when determining whether continuing the agreement serves American national-security interests.

Iran maintains that the United States must honor the agreement as negotiated and has warned against attempts to undermine it.

Congress Could Get the Decision

If Trump refuses certification, attention would quickly shift to Capitol Hill.

Congress would then have an expedited opportunity to consider legislation restoring sanctions suspended under the nuclear agreement.

Lawmakers would face a consequential choice.

Reimposing nuclear sanctions could severely damage the agreement and potentially place the United States at odds with Britain, France, Germany and the other countries that negotiated it.

Leaving the sanctions suspended, however, would mean the agreement could continue even after the American president formally declined to certify it under domestic law.

Trump could also seek changes to the agreement rather than immediately abandoning it.

Administration officials have suggested that the United States wants a broader strategy confronting Iran's missile program, regional activities and support for militant organizations.

A Decision With Consequences Far Beyond Washington

The approaching certification deadline represents far more than another dispute between Trump and the policies of his predecessor.

The nuclear agreement was designed to prevent Iran from developing a nuclear weapon while avoiding another military confrontation in the Middle East.

Its supporters argue that abandoning or weakening the agreement without evidence of a significant nuclear violation could eliminate restrictions that currently constrain Iran's program.

Its critics counter that the agreement merely postpones the problem while allowing Iran to benefit economically and continue other activities that threaten American interests and U.S. allies.

Trump must now decide which argument will guide American policy.

The president has spent more than two years describing the Iran agreement as unacceptable.

By October 15, he will have to decide whether the United States should continue certifying it.

And unlike campaign rhetoric, that decision could determine whether the nuclear agreement survives.

Source: White House statements, International Atomic Energy Agency reporting and contemporary reporting on the Iran nuclear agreement.