Trump has famously described the Joint Comprehensive Plan of Action as one of the worst agreements in American history. On the campaign trail he promised to tear it up as soon as he assumed office, but in the midst of his White House transition he has scaled back this rhetoric to refer instead to renegotiation. However, it is understood that this would be a serious challenge for the new president, owing to the multilateral nature of the agreement. This was highlighted on Tuesday by Helga Schmid, the secretary general of the European Union’s foreign policy service, according to Reuters.

The JCPOA negotiations were concluded in July 2015, with participation from Iran, the United States, the United Kingdom, France, Germany, Russia, and China. It was not signed by the participants but is understood to be binding upon all seven as long as each country remains a publicly-declared party to the agreement. The formal cancellation of the agreement would require consensus from all seven parties, but either the US or Iran could conceivably walk away from the agreement without notice, and indeed Iran has repeatedly threatened to do this if it decided that the US had violated the letter or the spirit of the agreement, as by imposing new sanctions, even on non-nuclear issues.

On the American side, critics of the agreement have accused the Iranians of not living up to their own obligations under the agreement. Some such critics have suggested that this could be grounds for Trump to cancel the agreement, or at least grounds for the imposition of penalties on the Islamic Republic. In fact, certain violations are known to have occurred, including two separate instances in which Iran exceeded the limits imposed by the JCPOA on its stockpiles of heavy water, a component of plutonium enrichment. These violations have been treated as insignificant by the Obama administration, which provided Iran with time to correct them and in one case directed the Department of Energy to purchase excess heavy water.

At a minimum, many of Trump’s supporters and team members are expecting an end to this conciliatory enforcement approach after he takes office. In fact, Rex Tillerson, Trump’s nominee for Secretary of State, said in a recent confirmation hearing that he would use the office to order a top-to-bottom review of the JCPOA, with an eye toward strengthening and fully utilizing its enforcement mechanisms.

This sort of strengthening would supposedly address a situation in which Iran is seen as taking advantage of the new international environment and facing no consequences. The excess heavy water stockpiles are only one sort of example of this. Western Journalism highlighted another on Tuesday when it quoted Olli Heinonen, a former head of the International Atomic Energy Agency, as saying that Iran was in the process of acquiring an unjustifiable surplus of raw uranium. The JCPOA imposes no restrictions on the Islamic Republic over this acquisition, limiting only the amount and level of enriched uranium that the country may possess at any given time. But Heinonen observes that the quantities of non-enriched material Iran is seeking to obtain are enough to fill its power generation and medical needs for over 15 years. This naturally inflames suspicions that the Iranians are positioning themselves to have greatly expanded nuclear capability once the agreement expires or once Iran or the US decides to walk away from it.

Part of this acquisition was undertaken with the explicit blessing of the Obama administration, thus giving Trump’s supporters one last piece of ammunition in their attacks on his handling of the Iran nuclear issue. But at the same time that Tehran was taking advantage of Obama’s willingness to look the other way on these controversial activities, the Iranians also indicated that they were taking steps to ship enriched uranium to Russia in order to bring them into compliance with defined limits under the JCPOA. Some analysts and Trump supporters view this as a likely reaction to the incoming president’s change in tone from that of his predecessor. The removal of enriched uranium seems at odds with statements that had been made by Iranian officials in recent weeks, suggesting for instance that the country would restart nuclear-powered submarine programs as direct retaliation for the congressional renewal of the Iran Sanctions Act.

If Iran is indeed changing its behavior with regard to the JCPOA, it may be a reaction to the sentiment expressed by Reince Priebus, Trump’s chief of staff. The Wall Street Journal quoted him as saying that he believes the nuclear deal to be “on life support.” On one hand, this could be seen as a more delicate repeat of Trump’s earlier threats to tear up the deal. But on the other hand it could alternatively be viewed as implying that with more rigorous enforcement of the existing deal, the Trump administration will have ample justification for re-imposing sanctions in response to the sorts of Iranian violations already witnessed, thereby possibly prompting Tehran to withdraw from the deal.