WASHINGTON (AP) – The United States said Tuesday it will give Iran “a little bit of space” to consider a package of incentives and threats meant to avert a nuclear standoff, but repeated that the offer is not open-ended.

“It’s a matter of weeks, not months,” State Department spokesman Sean McCormack said, echoing the vague deadline set out by Secretary of State Condoleezza Rice before the package was presented to Tehran.

U.S. officials would not discuss specifics of the package, saying that Iran needs time to review it and ask questions in private. They also would not characterize the initial, noncommittal response from Iran’s top nuclear negotiator.

“We want to give this every opportunity to succeed,” McCormack said. “The diplomacy, I would say, is at a sensitive stage,” he added. “We want to give them a little bit of space to consider what’s in the package, both on the positive as well as the negative side.”

The package includes a promise of western technical help in developing peaceful civilian nuclear energy if it stops enriching uranium, a waiver of U.S. legal restrictions to allow export of some agricultural technology, access to U.S. aircraft parts to upgrade Iran’s aging fleet and U.S. and European backing for Iran to join the World Trade Organization, diplomats and others said.

The proposal was agreed on last week by the United States, Britain, France, China and Russia _ the five veto-wielding members of the U.N. Security Council, plus Germany. Those nations would be expected to move for Security Council sanctions such as travel and financial restrictions on Iranian officials if Tehran does not take the deal or if negotiations fell apart.

Western officials described the package on condition of anonymity because negotiations among the six nations presenting it were private, and because Iran had not yet replied.

European Union foreign policy chief Javier Solana laid out the potential rewards and consequences in a visit to Tehran.

Top Iranian nuclear negotiator Ali Larijani said the initiative contains “positive steps” but also some “ambiguities.”

Rice was expected to speak by phone with Solana to discuss his visit and Tehran’s response, her spokesman said.

“There are robust measures on both sides, both the incentive side as well as the disincentive side,” McCormack said. “It presents the Iranian government with a very clear choice on both sides of the road.”

The Bush administration would not say exactly how long they will refrain from discussing specifics of the package, but White House press secretary Tony Snow put the onus on Iran.

“If the Iranians agree to suspend enrichment-related and reprocessing activities, then we’ll be able to discuss more openly what the incentives are, and we certainly hope that that’s the case,” Snow said.