A British research group says Iran needs at least a year to produce its first nuclear weapon.
The London-based International Institute for Strategic Studies said in a report Wednesday that evidence showed "beyond a reasonable doubt" that Iran was seeking to produce nuclear weapons, should its leaders decide to take that step.
Iran denies its nuclear program is for anything but peaceful purposes.
The institute provided two scenarios in which Iran could produce nuclear weapons. One scenario takes a year; the other takes a little more than two years.
The IISS report said Iran's current stockpile of low-enriched uranium would be enough for one or two nuclear weapons.
But IISS said delays at Iran's Natanz facility due to technical trouble stemming from faulty centrifuge designs and sabotage from a Stuxnet computer virus have hampered Iran's development of uranium-enrichment technology.
The think tank also said that despite Iran's claims of self-sufficiency, it still depends on foreign supplies of certain enrichment materials and components that are difficult to obtain because of strict export controls.
The United Nations Security Council has imposed four rounds of sanctions on Iran in an effort to force the country towards more transparency about its nuclear program.
Some information for this report was provided by AFP and Reuters.