The report by the institute founded by nuclear expert David Albright offers a more temperate view of Iran's nuclear program than some of the heated rhetoric that has surfaced since the United States and its allies stepped up sanctions on Tehran.
The Isis analysis is revealed after a prediction that Israel will attack Iran in 2012 to try and stop any nuclear bomb programme.
"Iran is unlikely to decide to dash toward making nuclear weapons as long as its uranium enrichment capability remains as limited as it is today," the report said.
The US and Iran are engaged in a war of words over sanctions, with Tehran threatening to retaliate by blocking oil shipping traffic through the Strait of Hormuz. The United States has said it will not allow that to happen. There are concerns the situation might spiral into a military confrontation that neither side wants.
The Isis report, financed by a grant from the United States Institute of Peace, says Iran had not made a decision to build a nuclear bomb.USIP is an independent, non-partisan centre created by the US Congress in 1984 that receives federal government funding.
Guardian News Service