Mohamed ElBaradei, director general of the International Atomic Energy Agency, said Iran sees nuclear weapons as an "insurance policy" against perceived threats from neighbouring countries or the United States.
Iranian President Mahmoud Ahmadinejad's disputed re-election has cast doubt on Western powers' hopes of a new dialogue with Iran over its nuclear programme, which Iran says is peaceful rather than military.
"My gut feeling is that Iran definitely would like to have the technology … that would enable it to have nuclear weapons if they decided to do so," ElBaradei told the BBC. "It wants to send a message to its neighbours, it wants to send a message to the rest of the world: yes, don't mess with us, we can have nuclear weapons if we want it.
"But the ultimate aim of Iran, as I understand it, is that they want to be recognised as a major power in the Middle East and they are.
"This is to them the road to get that recognition to power and prestige and … an insurance policy against what they heard in the past about regime change, axis of evil."
Ahmadinejad indicated on Sunday that there would be no change in nuclear policy during his second term, saying the issue "belongs in the past".
Six countries, including European Union members Britain, France and Germany, have offered Iran economic and other incentives if it stops enriching uranium, a process that can make fuel for power plants or weapons.
Iran says it wants nuclear technology to generate electricity.
Supporters of Iran's defeated presidential candidate Mirhossein Mousavi plan a fifth day of protests on Wednesday over the legitimacy of the election.
