TEHRAN, Iran — Iran’s nuclear program remains unchanged, a government spokesman Saturday, indicating that Tehran has no plans to meet a key Western demand that it stop enriching uranium.

Gholam Hossein Elham’s insistence that Iran would not change the central part of its controversial program came a day after Iran sent the European Union its response to an international proposal to curb its program in exchange for economic incentives. The content of the response has not been made public.

“Iran’s stand regarding its peaceful nuclear program has not changed,” Mr. Elham told reporters.

Iran’s ambassador to Belgium presented the response to the package to EU foreign policy chief Javier Solana in Brussels on Friday, and Iran’s top nuclear negotiator, Saeed Jalili, spoke with Mr. Solana by phone, Iranian state media has reported.

European officials said they were studying the Iranian response and were consulting among themselves and with America, Russia, and China on what to do next.

A positive response could open the way to renewed negotiations that might help cool recent sharp exchanges between officials on both sides. In recent weeks America and Iran have traded threats and warnings over possible American or Israeli military action.

But one European official cautioned about possible progress on the issue, and Mr. Elham’s comments did not indicate that a breakthrough was made.

“It was not something that made us jump up and down for joy,” said the official. “We are in a holding mode until we get a chance to look at it more closely. The official spoke on condition of anonymity because the information was confidential.

Mr. Elham also said Iran was ready to negotiate on its program “within the framework of the international rules and regulations.” He did not elaborate, but Iranian state media reported Friday that Messrs. Solana and Jalili agreed during their conversation to hold the latest in a series of talks in the second half of July.

Acting on behalf of the five permanent members of the U.N. Security Council and Germany, Mr. Solana offered the modified package of economic incentives to Iran during his June visit to the country. The offer is meant to persuade Iran to halt enrichment, which the six world powers fear Iran could use to produce weapons.

Iran has repeatedly insisted it will not give up enrichment, saying its only aim is to produce nuclear power, not weapons. But it had said the incentives package had some “common ground” with Tehran’s own proposals for a resolution to the standoff.

Separately, EU nations also approved new sanctions against Iran in June, imposing additional financial and travel restrictions on a list of Iranian companies and experts, including the country’s largest bank.

The six nations — America, China, Russia, France, Britain and Germany — first offered a package of economic, technological and political incentives to Tehran nearly two years ago on condition that it suspend enrichment.

The standoff has led to increasingly tense exchanges about the possibility of a military strike by Israel or America. An Israeli military exercise last month was seen as a warning to Iran.

The commander of Iran’s elite Revolutionary Guards has said that Iran would consider any military action against its nuclear facilities as the beginning of a war. However, the general also has said he thinks a strike by Iran’s adversaries is unlikely.