The Israelis, who have delivered veiled threats of a military strike, say they believe that Iran has restarted these “weaponization” efforts, which would mark a final step in building a nuclear weapon. The Germans say they believe that the weapons work was never halted. The French have strongly suggested that independent international inspectors have more information about the weapons work than they have made public.

Meanwhile, in closed-door discussions, American spy agencies have stood firm in their conclusion that while Iran may ultimately want a bomb, the country halted work on weapons design in 2003 and probably has not restarted that effort — a judgment first made public in a 2007 National Intelligence Estimate…

In the case of the plant outside Qum, designed for uranium enrichment, some nuclear experts speculate that it is only part of something larger. But a senior American official with access to intelligence about it said he believed the secret plant was itself “the big one,” but cautioned that “it’s a big country.”

This distinction has huge political consequences. If Mr. Obama can convince Israel that the exposure of the Qum plant has dealt a significant setback to the Iranian effort, he may buy some time from the Israelis.