Iran's controversial heavy water facility at Arak. (Hamid Foroutan/AFP/Getty Images)

Iranian Foreign Minister Javad Zarif told the country's legislature Wednesday that Iran will continue construction at its controversial nuclear facility at Arak, according to Reuters. A key provision of Iran's recent nuclear agreement, sealed just this weekend in Geneva with the United States and five other world powers, requires it to halt all "activities" at Arak. Zarif's announcement, though not an outright contradiction of this agreement, pushes Iran's interpretation right up to the limits of the deal. But the question of how much this matters, if it matters as all, is complicated.

The facility at Arak, which Iran insists is peaceful but could be used to make plutonium once finished, has been one of the key sticking points of the nuclear negotiations. Two weeks ago, French diplomats had scuttled an earlier round of talks, partly over objections that the deal being discussed did not adequately address Arak. This weekend's deal, an interim agreement meant to be a major step toward a more permanent resolution of the years-long Iranian nuclear crisis, forbids Iran from any nuclear-related activities at Arak for six months.

"The capacity at the Arak site is not going to increase," Zarif told Iran's legislator, according to a translation of his comments on Iran's Press TV. He went on, "It means no new nuclear fuel will be produced and no new installations will be installed, but construction will continue there."

Zarif's suggestion that Iran can continue construction at Arak does not appear entirely consistent with Western statements on the Geneva agreement. A "Joint Plan of Action" describing the deal, released by European Union High Representative Catherine Ashton on behalf of all parties at the talks, announced that Iran "will not make any further advances of its activities at the Natanz Fuel Enrichment Plant, Fordow, or the Arak reactor."

A White House release described the deal as including a provision that "Iran has committed to no further advances of its activities at Arak." To be fair, though, while the White House release goes into great detail about the sorts of nuclear-related work that are barred, it never explicitly says that all construction work of any kind is barred.

Civil construction work itself is not particularly significant in terms of Iran's nuclear capabilities. The country has been working on the Arak facility since the 1990s and has been repeatedly hobbled by setbacks, including an inability to secure key components. Progress on the nuclear components has been slow and fitful at best. So it's difficult to see basic civilian construction as particularly consequential in terms of nuclear capabilities.

"I anticipated this," Mark Hibbs, a nuclear proliferation expert at the Carnegie Endowment for International Peace, told me when I asked him about Zarif's announcement. "Likely step by Zarif to calm down hard-liners. Essential stuff is frozen. If they do excavation and civil construction around the reactor I don't care."

Western negotiators may well not care either, and perhaps may even have expected this. The language in the deal, after all, is extremely specific on limiting nuclear-related activities at Arak but strangely vague on whether civil construction is allowed. They may view Zarif's statement today with some sympathy.

On the one hand, Iranian officials who want a viable, long-term accord with the United States and other Western countries have to consider opposition from Iran's hard-liners. So it's certainly plausible that Zarif's announcement is meant to mollify internal opposition without taking any steps that might upset Western countries.

On the other, a key part of the process in working toward any long-term deal will be trust-building, which is no small thing given that the U.S. view is that Iran has cheated on past agreements. So the symbolic importance of civilian construction at Arak, even if it's just ditch-digging, is not nothing.