The head of the UN's nuclear watchdog has warned that resorting to military action against Iran over its nuclear programme would be "an act of madness".
Mr ElBaradei called for a "time out" with Iran
Mohammed ElBaradei also said Iran was close to reaching large-scale levels of uranium enrichment without providing assurances its programme was peaceful.
Enriched uranium can be used to fuel nuclear reactors but can also be made into nuclear weapons material.
The West has accused Iran of seeking nuclear weapons, a charge Iran denies.
Mr ElBaradei, the head of the International Atomic Energy Agency (IAEA) , said the stalemate between Iran and the UN Security Council was leading to confrontation.
He said any use of force to shut down Iran's nuclear programme "would be catastrophic, it would be an act of madness, and it would not solve the issue".
'Freeze for peace'
The United States and Israel have not ruled out the possibility of using military force against Iran if it does not scrap its uranium-enrichment programme.
But the US favours a diplomatic track, with what Secretary of State Condoleezza Rice has called "disincentives for Iran to continue its activities".
Mr ElBaradei called on Iran to freeze the expansion of its programme, saying the country was close to running 3,000 uranium-enrichment centrifuges.
IAEA officials say 3,000 centrifuges is the point of no return in an industrial programme.
Iran has said it hopes to install tens of thousands of centrifuges for industrial-scale enrichment at its Natanz site.
The uranium enrichment facility at Natanz
"On the one hand Iran is building the capacity and knowledge with regards to sensitive technology," Mr ElBaradei said.
"On the other hand the agency is unable to provide the assurance that this is a peaceful programme.
"It would be good if Iran today would stop building additional centrifuges and installing [them] in Natanz."
That could allow a "time-out or freeze for peace", he said.
Mr ElBaradei was speaking at a meeting of the agency's 35-nation board.
The Iranian envoy to the meeting repeated Tehran's position that it would not suspend uranium enrichment.
The UN Security Council has twice imposed rounds of sanctions on Iran for not suspending enrichment.
Mr ElBaradei said his inspectors had been unable to verify whether the centrifuges at Natanz were running at 100% efficiency or whether some might have crashed, as has happened before.
He repeated his estimate that Iran was three to eight years away from building a nuclear weapon, if that is what it was trying to do.