CNN - The Trump administration is extending waivers that allow countries signed up to the Iran nuclear deal to participate in civil nuclear projects with Tehran, but it's tightening the terms in an effort to increase pressure on the Iranian regime.

The US will extend waivers that allow the remaining parties to the 2015 deal to conduct research and do non-proliferation work at three sites in Iran without fear of facing sanctions, according to a fact sheet released by the State Department on Friday.
However, the waivers will be reduced from 180 days to 90, and State Department spokesperson Morgan Ortagus said in a statement that "assistance to expand Iran's Bushehr Nuclear Power Plant beyond the existing reactor unit could be sanctionable." Bushehr is one of the three facilities exempted from sanctions along with Arak and Fordow.

The US will also revoke two waivers that allowed Iran to ship its excess heavy water for storage and swap its enriched uranium for natural uranium, according to Ortagus.

"The decisions today enhance our ability to constrain Iran's nuclear program while pursuing maximum economic pressure," Brian Hook, the State Department special representative on Iran, told CNN in an interview Friday.
Internal debate

Behnam Ben Taleblu, a senior fellow at the Foundation for Defense of Democracies, said the administration "should continue take a nuanced view towards each waiver and facility. Keeping or terminating all waivers would have been a mistake."

The waivers will also, for the time being, avoid a clash with allies and partners who remain in the nuclear deal. Had the waivers ended completely, countries such as China, France, Russia, Germany and the UK as well as the EU would have faced the stark choice of either violating the terms of the nuclear deal -- giving Tehran another reason to walk away -- or face US sanctions.
The provisions allowing for civil nuclear cooperation in the deal are meant to reduce the proliferation risks of Tehran's nuclear program.

"We are permitting the temporary continuation of certain ongoing nonproliferation projects that constrain Iran's nuclear activities and that help maintain the nuclear status quo in Iran until we reach a comprehensive deal that resolves Iran's proliferation threats," the State Department fact sheet said.

The waivers allow modifications that ensure that the Arak reactor produces less plutonium, that the underground Fordow nuclear site can continue to be converted into a research facility, and that Iran can still buy the fuel it needs to run the reactor at Bushehr and produce electricity.
The question of nuclear waivers has garnered less attention than the administration's decision to end waivers that allowed countries to import Iranian oil on May 2, but has been the subject of intense debate within the administration and lobbying from outside parties.

Hawkish lawmakers have been pushing for an end to the nuclear waivers, arguing such a move could intensify the administration's "maximum pressure" campaign against Tehran. Within the administration, national security adviser John Bolton has pushed for an end to the waivers, according to an administration official and a source familiar with those discussions, while Secretary of State Mike Pompeo had opposed the move to completely end them, a former administration official told CNN.

The internal administration discussions had also prompted concerns among career State and Treasury Department officials who worried that revoking the waivers could eliminate important safeguards on Iran's nuclear program.
That's the argument arms control groups also make, saying that undermining the nuclear waivers could damage non-proliferation efforts and lead to the collapse of the Iran nuclear agreement.
"Failure to grant the waivers would jeopardize US nonproliferation priorities and increase the risk that he nuclear deal, known as the Joint Comprehensive Plan of Action, will collapse," the Arms Control Association said in a policy briefing on Monday.
The administration has been focused on steadily ratcheting up the economic and diplomatic pressure on Iran over the last year, a campaign that's meant to change Tehran's "behavior" administration officials say. In April, the US took the unprecedented step of designating Iran's Revolutionary Guard Corps as a foreign terrorist organization.
The designation opens the possibility that anyone doing business with the group, which has broad reach in Iran's economy, could face criminal charges for supporting a terrorist group. The move was the first time the US has declared that part a foreign government is a terrorist organization, administration officials said.

CNN's Jeremy Diamond and Zachary Cohen contributed to this report