TEHRAN,Iran – Iran’s president mocked a package of incentives to suspend uranium enrichment, saying yesterday they were like giving up gold for chocolate – defiance that appeared certain to complicate American efforts to curb Tehran’s nuclear ambitions.

“Do you think you are dealing with a 4-year-old child to whom you can give some walnuts and chocolates and get gold from him?” President Ahmadinejad asked derisively.

He spoke before a huge crowd in the city of Arak, the site of a heavy-water reactor that is scheduled for completion by early 2009. Such facilities produce plutonium as a byproduct usable in building nuclear weapons.

Signaling the difficulties ahead, a high-level, six-nation meeting on Iran was postponed yesterday, reflecting differences between America and its allies on one side and the Chinese and Russians on the other.

The London meeting of senior officials from the five permanent Security Council members and Germany was to have been held Friday, but was postponed to Tuesday at the earliest, diplomats told the Associated Press.

The British Foreign Office said the move was “to allow a further detailed preparation of the … offer to Iran.”

China and Russia have opposed bringing Iran’s case to a vote in the U.N. Security Council, where America, Britain, and France have pressed for sanctions.

Only a day earlier, European nations said they might add a light-water reactor to a package of incentives meant to persuade Tehran to give up enrichment permanently.

But Mr. Ahmadinejad heaped scorn on the offer in the nationally televised speech yesterday.

“They say they want to offer us incentives,” he said. “We tell them: Keep the incentives as a gift for yourself. We have no hope of anything good from you.”

His defiance was met with shouts of, “We love you Ahmadinejad!” from the crowd.