IRAN: Iran could secure a nuclear bomb in about five years if it makes a determined dash to acquire the weapon, according to the London-based International Institute for Strategic Studies.
But the institute, whose researchers visited Iran's nuclear facilities, said the more likely timescale was 10 to 15 years.
The institute's predictions are in line with the UK government's private assessment.
The Israeli government has warned that the timescale is shorter and that Iran will reach a point of no return later this year.
The US and Israel, supported by a separate diplomatic initiative by Britain, France and Germany, are trying to persuade Iran against enriching uranium, the first step towards achieving a nuclear weapons capability.
Iran is to be debated in a fortnight by the board of the International Atomic Energy Agency, the UN watchdog, which is likely to refer the issue to the UN Security Council.
John Chipman, director of the institute, said the intentions of Iran, which claims its nuclear ambitions are purely for civilian purposes, were not yet clear. But it appeared at least several years away from producing enough fissile material for a nuclear weapon.
He said Iran's present activity could see it secure a facility at the Natanz nuclear plant that would take about two to three years of operation to produce enough weapons-grade uranium for a single weapon.
The alternative would be for Iran to adopt a longer timescale, about a decade, and acquire a bigger capacity, in which case it could produce enough weapons-grade uranium within weeks, even days.
Gary Samore, director of studies at the institute, said it would be up to the Security Council to act decisively, possibly calling on Iran to comply with earlier IAEA resolutions.