Updated

The United States prodded Iran on Thursday to respond as early as next week — and no later than mid-July — to an offer of incentives to suspend its disputed nuclear program.

The Bush administration is reluctant to set a specific deadline for an Iranian response. But National Security Adviser Stephen Hadley said it would be "helpful and useful if we could get a response and know where the Iranians are" before foreign ministers of major countries meet in Moscow on June 29 and world leaders gather in St. Petersburg on July 15.

Iran's president said Wednesday that his country would take until mid-August to respond to the incentives package designed to halt its development of what the United States fears are nuclear weapons. That prompted President George W. Bush, who is traveling in Europe, to accuse Tehran of dragging its feet.

The foreign ministers' meeting and the gathering of world leaders are part of the annual summit of wealthy industrialized nations.

"Obviously it would be helpful to have a response before that set of meetings associated with the G-8 to come forward," Hadley said, briefing reporters during Bush's visit to Budapest, Hungary. "What we need is an authoritative response."

The U.S. and its partners are holding open the option of seeking a U.N. Security Council resolution to force Iran's hand if Tehran does not respond or if its response is unacceptable.

By making a public show of unity with the Europeans, Russians and Chinese, the administration is both signaling Tehran there is little to be gained by trying to promote division and also closing ranks for any U.N. drive for sanctions against Iran.

Iranian President Mahmoud Ahmadinejad said Wednesday that his country would respond in mid-August to the package of incentives. The U.S. and its partners have said they wanted a response within weeks not months.

The decision to stick to the original schedule the partners gave Iran — a response by next week or the partners begin plotting action at the U.N. — was reaffirmed quickly after Ahmadinejad's statement in a round of telephone calls by Secretary of State Condoleezza Rice and other diplomats.

Setting a calm tone at a U.S.-European summit in Vienna, Austria, Bush calmly disputed Ahmadinejad's timeline, saying it "seems like an awfully long time" to respond.

The offer by the five permanent U.N. Security Council members plus Germany seeks to persuade Tehran to suspend uranium enrichment in return for incentives, which would include the U.S. providing Iran with peaceful nuclear technology as well as joining in direct negotiations with Tehran.

"It shouldn't take the Iranians that long to analyze what is a reasonable deal," Bush said. "We'll come to the table when they verifiably suspend. Period."

The State Department, also taking a gentle line, suggested that if Iran had questions about the package, Iranian nuclear negotiator Ali Larijani could submit them to senior European diplomat Javier Solana.

This offer, made during the daily department media briefing on Wednesday, is far short of a take-it-or-leave-it stance. Still, Bush made it clear that there will be no budging on the U.S. demand that Iran suspend uranium enrichment and submit to verification that it has followed through.

In a calculated show of unity, top U.S., European and Chinese diplomats exchanged telephone calls. Undersecretary of State Nicholas Burns, the U.S. point man on the Iranian nuclear issue, and his counterparts in the British, French, German, Chinese and Russian governments also conferred by phone and agreed that Iran should accept the offer "within weeks, not months," State Department deputy spokesman Adam Ereli said.

The foreign ministers of the G-8 industrialized democracies are due to meet in Moscow next Thursday, which coincides with the drive for a reply from Tehran within a week's time.

China, which could play an opposing role in the Security Council and is not part of the G-8, called on Iran to earn international trust.

"Iran needs to use real actions to win the confidence of the international community," Foreign Minister Wen Jiabao said during a visit to South Africa.

Uranium enrichment can produce either fuel for a nuclear reactor or material for a warhead. Iran says it is pursuing peaceful energy generation. The United States and some Europeans accuse Iran of seeking to develop nuclear weapons.