Updated

Iran said Tuesday it was ready for "serious negotiations" on its nuclear program, but a semi-official news agency reported the government was unwilling to abandon nuclear enrichment — the key U.S. demand.

Ali Larijani, the country's top nuclear negotiator, delivered a written response to ambassadors of Britain, China, Russia, France, Germany and Switzerland to a package of incentives aimed at persuading Iran to roll back on its nuclear program.

Larijani refused to disclose whether the response included an offer to suspend uranium enrichment, and no details of Iran's response were released. The state-run television quoted Larijani as telling the diplomats Iran "is prepared as of Aug. 23rd to enter serious negotiations" with the countries that proposed the incentives package.

But the semi-official Fars news agency reported that Iran rejected calls to suspend "nuclear activities" — or uranium enrichment — and "instead has offered a new formula to resolve the issues through dialogue."

CountryWatch: Iran

Iran delivered its response to the incentives offer nine days before a U. N. Security Council deadline for Iran to halt uranium enrichment or face economic and political sanctions.

The White House deferred comment on the Iranian government's response.

"The Security Council's deadline is Aug. 31. I'm not going to parse the Iranian government's document today here on the airplane," White House deputy press secretary Dana Perino said on Air Force One as President George W. Bush flew to an appearance in Minnesota. "That is a job best left to the diplomats."

She said the U.S. government has received a copy of the document, but that she doesn't believe the president had seen it yet.

"We are aware of the rhetoric that has been coming out of the regime about a nuclear program and the president made very clear to everyone yesterday in his press conference that he thinks that that would be a mistake and dangerous for the region and the whole world," she added. "So let's let the diplomats take a look at this response before we parse it out too much here."

The European Union's foreign policy chief, Javier Solana, said the Iranian document was "extensive" and required "a detailed and careful analysis." He did not elaborate or provide any details.

In New York, the U.S. ambassador to the United Nations, John Bolton, said Washington will "study the Iranian response carefully" but was prepared to move forward with sanctions against Tehran if its response to the incentives package was not positive.

Tuesday's announcement was the latest development in the yearlong standoff between Western countries and Iran over Tehran's nuclear program. Iran insists the program is for peaceful purposes, but the United States and other countries suspect Tehran is trying to build a nuclear arsenal.

Last month, the Security Council set an Aug. 31 deadline for Iran to halt uranium enrichment or face economic and political sanctions.

Iran called the resolution "illegal" but had said it was willing to offer a "multifaceted response" to the incentives package that the United States, the four other permanent council members and Germany offered to Tehran in June.

Iranian officials familiar with Larijani's response said Tehran offered a "new formula" to resolve the dispute. The officials spoke on condition of anonymity because of the sensitivity of the information.

"Iran has provided a comprehensive response to everything said in the Western package. In addition, Iran, in its formal response, has asked some questions to be answered," one official said without providing more details.

At the same time, however, the Iranians have been signaling they are not prepared to abandon nuclear enrichment — a component in manufacturing nuclear weapons — as a precondition to talks. Last month, a senior Iranian lawmaker said the country's parliament was preparing to debate withdrawal from the Nuclear Nonproliferation Treaty if the U.N. Security Council adopts a resolution to force Tehran to suspend uranium enrichment.

However, if the Iranians left the door open to halting enrichment as talks progressed, that would drive a wedge between the American, British and French on one side and the Russians and Chinese on the other.

Last month, Russia said the Security Council was in no rush to pressure Iran over its nuclear program, striking a more conciliatory tone than the United States.

On Monday, Iran's supreme leader, Ayatollah Ali Khamenei, said the Islamic Republic "has made its own decision and in the nuclear case, God willing, with patience and power, will continue its path."

Khamenei accused the United States of putting pressure on Iran despite Tehran's assertions that its nuclear program was peaceful.

Furthermore, Iran prevented inspectors from the U.N. nuclear agency from inspecting an underground site meant to shelter its uranium enrichment program from attack. The head of the International Atomic Energy Agency, Mohamed ElBaradei is to report by Sept. 11 to the agency's board on Iran's compliance with the U.N. deadline to freeze enrichment and other aspects of Tehran's cooperation with U.N. inspectors.

In February, Iran for the first time produced its first batch of low-enriched uranium, using a cascade of 164 centrifuges. The process of uranium enrichment can be used to generate electricity or in building a bomb, depending on the level.

The Western incentives package has not been made public but some details have leaked. They include an offer to lift a ban on sales of Boeing passenger aircraft, providing Iran with some nuclear technology to build reactors for civilian purposes and guaranteeing a supply of nuclear fuel.

Iran has pursued a confrontational stand on the nuclear issue following the election of President Mahmoud Ahmadinejad last year. The hardline president has insisted that Iran has a right to pursue nuclear technology despite threats of sanctions.

Ahmadinejad has used the nuclear issue to encourage a sense of national pride among Iranians by standing up to the United States and other Western countries.

The failure of Israel to destroy the pro-Iranian Hezbollah movement in the 34-day war in Lebanon may embolden hard-line groups within Iran to risk a showdown with the Americans, who are bogged down in neighboring Iraq.