Britain, France and Germany, chief negotiators with Iran, had planned to offer the package after the UN Security Council approved a resolution demanding that Iran halt nuclear activities the West believes are a cover for bomb making.
But with that resolution now at an impasse, major powers authorised the three Europeans, known as the EU3, to work on the revised package-intended to present Iran with clear choices of benefits and penalties-while negotiations on the resolution continue, European diplomats said.
"People will explore what are the triggers, whether there are triggers," British Foreign Secretary Margaret Beckett told a small group of reporters. The Iranians had to realise "they don't need to carry on with it because there are ways to do what they say they want".
"What is the exact nature of something that could perhaps give them that way out? That is exactly what everybody will be exploring," Beckett said.
The key difference is that unlike a previous package offered to Iran by the EU3 last year, the Europeans aim to get the United States, Russia and China on board as partners.
There would be specific commitments to back sanctions if the economic and political inducements do not persuade Iran to abandon weapons-related pursuits, said a European diplomat who spoke on condition of anonymity.
Foreign ministers from the five permanent UN Security Council members and Germany met for two hours on Monday as a group and then again in one-on-one meetings on Tuesday.
Senior officials of the six had a follow-up meeting on Tuesday, and authorised the EU3 to prepare a package of benefits and punitive action that would be refined in Brussels on Monday, according to European diplomats at the meeting.
Some of the elements are similar to those the three Europeans had already drawn up, including energy, security and civilian nuclear power.
Late on Monday, France's Foreign Minister Philippe Douste-Blazy told reporters Iran, if it co-operated, could be rewarded with an "ambitious package-in the domain of civilian nuclear energy, in the domain of trade, in the domain of technology and-why not-in the security domain".
The United States previously had opposed a new offer to Iran insisting the security council must take strong action to ensure Tehran complies with demands to halt enrichment.
On the UN Security Council resolution, no agreement was reached among the ministers despite hours of talks. US and British officials said no vote was expected this week.
The resolution, drafted by France and Britain and backed by the United States, would order Iran to suspend its nuclear programmes immediately under Chapter 7 of the UN Charter, which makes an action legally binding.
Chapter 7, used in dozens of Security Council resolutions, allows for sanctions and even war, but a separate resolution is required to specify either step.
Russia and China fear too much pressure on Iran would be self-defeating or precipitate an oil crisis. Both worry the United States would use a resolution under Chapter 7 to justify military action.