THE INTERNATIONAL Atomic Energy Agency has now spelled out in detail what governments around the world have known for a long time: Iran’s nuclear program has an explicit military dimension, aimed at producing a warhead that can be fitted onto one of the country’s medium-range missiles. In a 14-page annex to its latest report, the agency summarizes the evidence behind its conclusion that “Iran has carried out activities relevant to the development of a nuclear explosive device.” It also says that these programs “may still be ongoing” — a contradiction of the U.S. intelligence community’s controversial conclusion that they were suspended in 2003.

The IAEA’s evidence, which includes 1,000 pages of documents, interviews with renegade scientists who helped Iran and material from 10 governments, ought to end serious debate about whether Tehran’s program is for peaceful purposes. That’s why Russia and China tried to block the report. Those governments would like to avoid the discussion that must now begin: what must be done to stop the program.

One option is military action, which Israel’s government appears to be debating. We continue to regard that as a last resort, and one that is not now justified. Military strikes would only slow — not eliminate — Iran’s work on a bomb, while risking a conflagration in the Middle East. Though experts are divided over how much time Iran still needs to gain all the elements for a weapon, it is likely at least a year or more away from completing one — and international inspectors might detect a final push.

So there is time, but the Obama administration and other Western governments must recognize that the sanctions they have so far put in place, and covert operations aimed at sabotaging Iranian centrifuges and killing scientists, have not succeeded in changing the regime’s intentions or stopping its work. The IAEA reports that uranium enrichment continues at a steady pace — 4.9 tons of low-enriched material have been produced, enough for four bombs with further processing. Just as disturbing: Iran continues to install centrifuges in a new underground facility and says it will step up production of higher-enriched uranium, which could be quickly converted to bomb-grade material.

The Obama administration has been saying since last month, when it revealed an Iranian plot to murder the Saudi ambassador to the United States, that it intended to press for tougher sanctions. But in briefing reporters this week, officials appeared to back away from measures that would have real impact — such as a Treasury ban on transactions with Iran’s central bank. Though that step has strong support in Congress, the administration is wary that, by effectively shutting down Iran’s oil exports, it would provoke a spike in energy prices that would damage the fragile global economy.

That is a legitimate concern. But President Obama has said repeatedly that Iran’s acquisition of a nuclear weapon is unacceptable — and the IAEA report makes clear the danger is growing, not diminishing. If Iran is to be stopped without the use of military force, the president, and the country, should be willing to bear some economic pain. The alternative — allowing Tehran to go forward — would be far more costly.