ASPEN, Colo. — The Trump administration is weighing a decision to end waivers that allow Iran to operate a civilian nuclear program with international assistance, in a move that would dismantle a key pillar of the 2015 nuclear deal between Tehran and world powers, according to two current U.S. officials and a former official familiar with the discussions.

The administration has been locked in an internal debate over the decision, and if carried out, the move could cause the unraveling of the international nuclear agreement that has been in jeopardy since President Donald Trump pulled the U.S. out of the deal last year.

The administration's discussions coincide with rising tensions between Iran and the United States and a series of incidents in the Persian Gulf, including the downing of a U.S. drone and an Iranian drone, attacks on oil tankers and the seizure by Iran on Friday of two commercial vessels in the Strait of Hormuz.

The Fordow facility in Iran appears in a satellite image from 2013. DigitalGlobe/Getty Images

European governments have urged the administration not to revoke the civilian nuclear waivers, fearing such an action could blow up the fragile accord entirely and trigger a chain of escalation with Iran in its standoff with the United States.

The waivers allow Iran to receive help from countries that signed up to the nuclear accord to run several atomic sites for civilian purposes, including adapting a heavy water reactor at Arak and converting a former uranium enrichment facility at Fordow into a medical isotope research center. The waivers for Arak and Fordow in particular have come under criticism from Republican lawmakers and advocates of a hawkish stance on Iran.

The White House, State Department and Treasury Department declined to comment.

The Trump administration in May renewed the civilian nuclear waivers for a 90-day period, after having issued waivers for 180 days previously. The State Department originally justified the waivers as a way of preventing Iran from pursuing nuclear weapons-related work.

Iran has long insisted on its right to a civilian nuclear program to generate electricity and conduct research. The nuclear agreement between Iran and six world powers, including the United States, allowed Tehran to retain a limited civilian nuclear program while imposing restrictions on any potential path to an atomic weapon.

Apart from waivers for the Arak and Fordow sites, the U.S. has also granted waivers to permit Iran to run its sole nuclear power reactor at Bushehr with Russian assistance and a research reactor in Tehran to produce medical isotopes.

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The nuclear deal, known as the Joint Comprehensive Plan of Action, or JCPOA, was designed to block Iran from developing nuclear weapons in return for easing U.S. and international economic sanctions.

Iran continued to abide by the deal for about a year even after Trump pulled the U.S. out of the accord. But Iran has begun breaching the terms of the deal in recent weeks, exceeding the limits on enriched uranium stockpiles and the levels of uranium enrichment.

Outspoken opponents of the nuclear deal in Congress, including Republican Sens. Ted Cruz, Marco Rubio and Tom Cotton, have been pushing the White House to end the waivers, citing Iran's recent actions as more proof that Tehran cannot be trusted and should not be receiving any international assistance for nuclear activities.

Sen. Cruz calls the site at Fordow "a military bunker the Ayatollahs dug out of the side of a mountain so they could build nuclear bombs" and has been demanding the administration stop permitting Tehran to conduct work there with outside assistance. "The Trump administration should immediately cancel the civil-nuclear waivers it has been issuing, which allow Iran to continue building up Fordow and other nuclear sites," Cruz said in a statement last week.

Iran kept the Fordow site in the mountains near the city of Qom secret until the United States, Britain and France publicly revealed the uranium enrichment center in 2009. Iran has denied it has any plans to develop nuclear weapons.

Another proponent of scrapping the waivers, Mark Dubowitz, chief executive of the Foundation for Defense of Democracies think tank, which has sharply criticized the nuclear agreement, argues that Iran's recent actions removed the rationale for maintaining the exception.

"The violations of the JCPOA have eliminated any justification for extending the waivers for having this kind of nuclear assistance and cooperation," Dubowitz said. "We should be doing everything possible to prevent Iran from enhancing its nuclear infrastructure which has been designed from the ground up to build nuclear weapons."

One Republican congressional aide told NBC News there is "enormous frustration" among GOP lawmakers in Congress that some officials inside the administration remained reluctant to revoke the waivers.

Arms control experts and former U.S. officials say the waivers allow the outside world to keep tabs on Iran's nuclear activities and to ensure work at sites such as Fordow does not veer into potential weapons-related projects.

"It is clearly in the U.S. and international interest to allow the continuation of projects at key nuclear sites that reduce Iran's nuclear weapons potential," said Daryl Kimball of the Arms Control Association.

Ending the waivers also would put the other governments that signed the deal, Britain, France, Germany, Russia and China, in a bind, Kimball said. Those countries — which have agreed to provide assistance on civilian nuclear projects — would have to decide whether to fulfill their commitments under the deal or risk U.S. sanctions, he said.

Scrapping the waivers could lead Iran to abandon the nuclear agreement entirely, and make it difficult for any future president to revive the deal, experts said. Most of the presidential candidates vying for the Democratic Party's nomination have said they would return the United States to the agreement.

Revoking the waivers would further escalate the crisis between Iran and could close the door to possible negotiations, said Dana Stroul, a former Pentagon official and congressional policy advisor.

"It raises questions about the intentions of the Trump administration," said Stroul, now a senior fellow at the Washington Institute for Near East Policy. "It suggests the actual intention is to tear down the JCPOA and make it collapse."