Mr. Annan told reporters in Vienna Friday he believes the proposed talks between European Union countries and Iran would be more productive if they included the United States.
The U.S. has refused to take part in direct talks, but has given its European allies some time to persuade Iran to halt all uranium enrichment activity or face possible U.N. sanctions.
Three EU countries - Britain, France and Germany - are preparing a package of incentives for Iran to give up its nuclear ambitions. The package is expected to be presented to Tehran within weeks.
Iranian President Mahmoud Ahmadinejad said Friday the nuclear standoff is "just psychological propaganda" aimed at threatening his country.
At a meeting with Islamic scholars in the Indonesian capital of Jakarta Friday, Mr. Ahmadinejad also dismissed the chances of military action against Iran over the nuclear issue.
The U.S. and much of the West suspect Iran of planning to build nuclear weapons. Iran says its nuclear program is for civilian energy use.
Some information for this report was provided by AFP and AP.