WASHINGTON -- The Trump administration is poised to renew waivers that allow Iran to receive international assistance for civilian nuclear projects, after a heated internal debate over whether to dismantle a key element of the 2015 nuclear deal, according to three sources familiar with the matter.

In what would be a setback for Iran hawks, Treasury Secretary Steven Mnuchin and other administration officials appeared to prevail in the policy argument against national security adviser John Bolton and Secretary of State Mike Pompeo, the sources told NBC News.

Proponents of keeping the waivers warned that removing them could force the United States to impose sanctions on Russian, Chinese and European firms assisting with nuclear work in Iran permitted by the nuclear accord, according to a U.S. official and a source familiar with the discussions.

The Treasury Department appealed for more time to work out the possible consequences if that scenario played out, the sources said.

The waivers for five nuclear sites in Iran are due to expire on Thursday, and an announcement from the administration is expected later this week.

The State Department declined to comment Tuesday night, and the White House was not immediately available for comment.

The plan to retain the waivers was first reported by the Washington Post.

President Donald Trump withdrew from the nuclear agreement between Iran and world powers, known as the Joint Comprehensive Plan of Action or JCPOA, last year. But since then, administration officials have continued to spar over how far to go in carrying out a “maximum pressure” campaign on Tehran.

The underlying argument that has played out at the White House over the past year hinges on whether the United States would have more leverage in any future talks with Iran by totally dismantling the 2015 deal, or whether it is better to preserve the accord as a starting point for negotiations, U.S. officials say.

Proponents of keeping the waivers believe “the best way to position for a new deal, is to keep the old deal around in the meantime,” one source said. “There is an active group within the State Department, Treasury Department and Energy Department that sees value in keeping the rump JCPOA alive.”

Britain, France and Germany had urged the White House to extend the waivers, saying that it was in the interests of the United States and Europe to ensure Iran stuck to a plan to convert various nuclear sites to civilian purposes.

Bolton and officials at the national security council disagree with the rationale for keeping the nuclear waivers, arguing Iran should not be allowed to preserve its nuclear infrastructure with help from the outside world.

They also play down the possibility that the U.S. would have to impose sanctions on Russian, Chinese or European companies engaged with Iran’s nuclear program, sources said. They cite an administration decision in May that barred two forms of international assistance for Iran’s nuclear activities involving Oman and Russia. In both of those cases, the two countries halted their cooperation and there was no need to for Washington to introduce U.S. sanctions.

Iran hawks in Congress, including 50 Republicans in the House and Republican senators Ted Cruz of Texas, Tom Cotton of Arkansas and Marco Rubio of Florida, had pushed for removing the waivers. At one point, they appeared to have the upper hand in the administration discussions earlier this month, the sources said.

But Trump appeared to come around to Mnuchin’s view in recent days, much to the frustration of advocates of a tough line on Iran inside and outside the administration.

“There were a hundred ways to cancel these nuclear waivers responsibly," said one U.S. official familiar with how the debate unfolded. “The State and Treasury teams rejected those options because their actual goal is to save the nuclear deal. So now we've got a situation where they've humiliated President Trump this round and set themselves up for a diplomatic crisis in the fall” when the new waivers expire, the official said.

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 other opponents of the 2015 deal.

The U.S. also has 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.

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.

The State Department declined to comment. The White House was not immediately available for comment.