TEHRAN, Iran -- Iran delivered a "constructive" preliminary response yesterday to a package of incentives meant to convince the nation to curtail parts of its nuclear program, European and Iranian officials said.

Iran's ambassador to Belgium delivered a letter signed by Foreign Minister Manoucher Mottaki to the office of European Union Foreign Policy Chief Javier Solana in Brussels late yesterday. Western diplomats declined to disclose details of either the letter or a phone conversation Mr. Solana had earlier in the day with Iran's chief nuclear negotiator, Saeed Jalili.

However, both sides described Iran's response as positive.

Iranian news media said the two sides agreed to resume negotiations by the end of the Iranian month of Tir, which falls July 21. But no European official could confirm such a timeline.

"The conversation was constructive," Solana spokeswoman Cristina Gallach said in an e-mail. "All the noises are positive."

Iran faces the prospect of a fourth round of U.N. Security Council sanctions for refusing to stop its enrichment of uranium ore, a process that can produce fuel for a power plant or, if highly concentrated, explosive material for a nuclear bomb.

Iran insists that its intentions are peaceful, but people in the West suspect otherwise. Backed by the United States and other world powers, Mr. Solana in June delivered a package of potential economic and political incentives meant to persuade Tehran to stop enriching uranium. Iran has offered its own package as a basis for compromise, but it does not mention the possibility of halting enrichment.

Iran is also considering a proposal from Mr. Solana under which it would stop adding new uranium-processing centrifuges, and the West would refrain from pushing for sanctions during a six-week period before negotiations.

Fears of a military confrontation between Iran and the United States or Israel have pushed oil prices to record highs.

In an interview published yesterday, the head of Iran's elite Revolutionary Guard said his country would consider any attack on its nuclear installations the beginning of a larger confrontation.

But while Iranian military officials have been painting dire scenarios in case of military action, diplomats have dramatically softened their rhetoric on the nuclear issue, even as Iran refuses to budge on the enrichment issue.

Critics in the United States say Iran is trying to run out the clock on the Bush administration without moving on enrichment, a strategy with which many Iranians concur.

"Further talks imply less pressure, fewer sanctions, lowered risk of war and a sort of grace period," said Nader Karimi Jouri, editor-in-chief of Siasat Rouz, or Today's Politics, a conservative daily often critical of the government's handling of economic matters.

For years, Iran has insisted on uranium enrichment as a basic right.