IRAN HAS TAKEN two more steps toward producing a nuclear weapon. According to a report released Friday by the International Atomic Energy Agency, it has begun to use a new, more advanced centrifuge to enrich uranium, which could allow it to produce bomb-grade material in a much shorter time period, should it choose to do so. It also has begun installing centrifuges in a facility dug into a mountain near the city of Qom, which could be nearly invulnerable to a U.S. or Israeli air attack. Iranian officials say those centrifuges will be used to triple the production of uranium enriched to 20 percent, creating a stockpile for which Tehran has no plausible legitimate use.

The report underlines the fact that, contrary to the impression often promoted by the Obama administration, the danger that Iran will become a nuclear power is growing, not diminishing. Administration spokesmen often speak of what they say has been the crippling effect on the Iranian economy of sanctions that have been stepped up during the past two years. Extensive media reports have told the sensational stories of computer viruses that may have disabled 1,000 or more Iranian centrifuges and assassinations that have eliminated several Iranian scientists.

The administration deserves credit for the diplomatic effort that produced stricter sanctions. But the grim reality is that Iran’s leaders have not been deterred from their goal of producing a weapon, and the project is making steady progress. Despite the loss of centrifuges, Iran’s rate of enrichment is nearly double what it was in 2009, according to a study by the Bipartisan Policy Center. The center estimates that, should Iran decide on a “breakout” strategy of rapidly producing the highly enriched uranium for a weapon, it could do so in as little as 62 days — and that by the end of next year that timeline could fall to 12 days, making it possible to produce the core material for a bomb between visits by international inspectors.

With its focus on the Arab Spring and other international challenges, U.S. policy hasn’t taken account of these developments; in fact, it appears adrift. The administration’s reaction to the new IAEA report was so low-key as to be virtually nonexistent. In the vacuum, others are offering bad initiatives. Russia has proposed that sanctions be lifted on Iran if it deigns to answer long-outstanding IAEA questions about explicitly military dimensions of its program, such as warhead designs. On Monday, Tehran played on this idea, offering five years of “full supervision” of its nuclear work if sanctions are ended.

The United States will surely oppose these plans. But it needs its own strategy for responding to Iran’s advances. Boasting about the effect of past measures is not enough when Tehran’s behavior remains unchanged.