THE PUBLIC outlining by Iranian Foreign Minister Mohammad Javad Zarif of his government’s negotiating position in the ongoing talks on its nuclear program was a tip-off that Tehran isn’t aiming to conclude a deal by the July 20 deadline. Instead, Mr. Zarif’s Monday interview with the New York Times, in which he described an Iranian position that was unacceptable to Western governments but better than Tehran’s previous, blatantly unserious offers, was designed to provide Iran’s interlocutors — and in particular the Obama administration — with a rationale for extending the talks for up to six more months.

“[W]e have made enough headway to be able to tell our political bosses that this is a process worth continuing,” Mr. Zarif cheerfully declared in Vienna on Tuesday, adding, “I am sure Secretary [of State John F.] Kerry will make the same recommendation.” He seemed to be right: While Mr. Kerry said “very real gaps” remained between Tehran and the six-nation coalition, his aides told reporters an extension was likely.

In our view, prolonging the negotiations is better than declaring a breakdown, which could lead to a military conflict at a time when the United States is already juggling multiple crises in the region and beyond. The preliminary accord struck with Iran last fall, while far from perfect, has appeared to succeed in curtailing Tehran’s enrichment of uranium. Contrary to predictions by Israel, the limited economic relief given in exchange has not caused the overall sanctions regime to break down.

Mr. Zarif’s maneuvering, however, supports two sobering conclusions. One is that the Iranian regime is not feeling as much economic pressure as it was a year ago and no longer sees the removal of sanctions as urgent. The other is that Tehran is positioning itself in such a way that it will be unable to make the concessions that should be required for a long-term settlement without a major climb-down and accompanying loss of face.

While some headway appears to have been made on issues such as Iran’s construction of a reactor capable of producing plutonium and terms for enhanced inspections, what looks like a nearly unbridgeable gulf has opened on the critical issue of uranium enrichment. The United States and its allies have sought a substantial reduction in Iran’s stock of 19,000 centrifuges , so that the time it would need to produce the material for a bomb would be extended to at least six months to a year. Supreme leader Ayatollah Ali Khamenei, in contrast, appears to have prohibited any dismantlement of existing infrastructure and delivered a speech this month declaring that Iran needs 190,000 centrifuges.

Iranian Foreign Minister Mohammad Javad Zarif. (Heinz-Peter Bader/Reuters)

Mr. Zarif said he was offering to extend the current controls on Iran’s enrichment — which freeze the current centrifuges in place and limit the amount and quality of their production — for a few years in exchange for the removal of sanctions. In addition to the problems that would be posed by a time limit, the deal would leave in place a bomb “breakout” capacity. That should be unacceptable.

It’s not inconceivable that Iran’s position will soften if talks continue. But the Obama administration should reject any attempt by Mr. Zarif to obtain concessions, such as increased oil sales, in exchange for an extension. And it should begin seriously preparing for the moment when time runs out — and when, as seems likely now, Iran refuses to yield.