...The package agreed on Thursday carries the threat of U.N. sanctions if Tehran remains defiant over what the West calls a rogue nuclear program that could produce a bomb. The United States, in a major policy shift, conditionally agreed this week to join those talks. It would be the first major public negotiations between the two countries in more than 25 years.

Rice met with the foreign ministers from the European nations that led talks with Iran, which stalled last year. European Union foreign policy chief Javier Solana, Russia's foreign minister and a deputy Chinese foreign minister also attended.

Russia and China might join in any future talks with Iran. Both hold vetoes in the U.N. Security Council, and the United States needs their cooperation to seek sanctions or other harsh measures.

The formal offer of talks are expected to be made by France, Britain and Germany - the three nations that previously negotiatiated with Tehran. A senior U.S. state department official said he expected Tehran would be invited to begin new negotiations "within a matter of days."

A short statement issued by foreign ministers from the six powers and the European Union did not mention economic sanctions, which the U.S. wants and Iran has tried hard to avoid.
        
The powers agreed privately, however, that Iran could face tough Security Council sanctions if it failed to give up unranium enrichment and other disputed nuclear activities, U.S. officials said.