Iran is not expected to be capable of producing nuclear weapons for at least a year, maybe more, U.S. Defense Secretary Robert Gates said on Tuesday.
Asked about reported comments that Iran might be able to join the nuclear club in months, Gates said: "I don't believe it."
"I think that most estimates that I've seen, haven't changed since the last time we talked about it, which is probably at least a year, and maybe more," Gates told reporters on a flight to South America.
Meanwhile, nations gathered at a summit in Washington pledged on Tuesday to block "non-state actors" from obtaining nuclear material for malicious purposes, one of a raft of measures to bolster global nuclear security.
A draft communique also called for new controls on highly enriched uranium and separated plutonium - key components of nuclear weapons - while recognizing that security steps should not infringe upon the right of states to develop peaceful uses of nuclear energy.
'Catastrophe for the world'
US President Barack Obama told delegations from 47 nations at the summit it was time for concerted global action to lock down loose nuclear materials and said if al-Qaeda got an atomic weapon it would be a "catastrophe for the world."
The communiqué set out a number of general commitments in which countries promised to step up protection of nuclear materials under their control.
It said one key objective was "to prevent non-state actors from obtaining the information or technology required to use such material for malicious purposes."
But, in a nod to some of the developing countries that are seeking to launch their own civilian nuclear programs, the summit also backed "strong nuclear security procedures that will not infringe upon the rights of states to develop and utilize nuclear energy for peaceful purposes."