"The Iranians miscalculated. They thought they could divide the United States from our European allies and Russia and China, but we've been able to craft a united coalition of all those countries," Burns told NBC television.

"They have to choose -- negotiations with us, or further action in the security council," Burns said.

He added: "Frankly, I think they're rather cornered and isolated. There are very few countries defending them and they're running out of options."

"We think this policy of patient diplomacy and crafting multilateral coalitions to tighten the pressure on them is going to work, and it's the right way to go clearly for the United States," Burns said.

Tehran is facing mounting international pressure to give a clear answer before the Group of Eight (G8) summit from July 15-17 on an offer of incentives from world powers in return for suspending uranium enrichment activities.

Iran said Sunday it will take until the second half of August to respond to the international package, which was drawn up by the five permanent Security Council members plus Germany and presented to Iran on June 6.

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