Intelligence officials from several countries say Iran in recent weeks has virtually completed an underground nuclear enrichment plant, racing ahead despite international pressure and heavy economic sanctions in what experts say may be an effort to give it leverage in any negotiations with the United States and its allies. …

The installation of the last of nearly 3,000 centrifuges at a site called Fordo, deep under a mountain inside a military base near the holy city of Qum, puts Iran closer to being able to build a nuclear weapon, or come up to the edge, if its leaders ultimately decide to proceed. …

Talks this year between Iran and the so-called P5-plus-1 — the five permanent members of the United Nations Security Council plus Germany — have made little progress. The New York Times reported Sunday that the United States and Iran had reached a tacit agreement to hold direct talks after the American presidential election. Mr. Obama denied the report but said in Monday’s debate with Mitt Romney that he was open to such talks.