Iran again warned the United States on Sunday against attacking its nuclear facilities, saying that it has tens of thousands of would-be suicide bombers at the ready and can count on the support of militants across the region.
Pope Benedict XVI also weighed into the dispute, appealing for "serious and honest" talks, to achieve "an honourable solution" for all parties.
"The United States should be aware that it is not in a position to create another crisis in the region," Iranian Foreign Minister Manouchehr Mottaki said.
"Iran has not excluded the possibility of an American aggression against it," Akbar Hashemi Rafsanjani also said during a visit to Syria. "Iran is undergoing psychological warfare, and is resolved to defend its rights," Rafsanjani said, adding that "the United States will not risk using force."
The Institute for Science and International Security, a Washington-based think-tank, said that satellite images showed that Iran has expanded and reinforced its main nuclear fuel processing facilities in Isfahan and Natanz, possibly to prepare them for a military strike.
Iran, buoyed by high oil prices and confident that US troops are bogged down in Iraq, appears confident that it can deter any sanctions or attack.
"You can start a war, but it won't be you who finishes it," General Yahya Rahim Safavi, head of Revolutionary Guards and among the regime's most powerful figures, said on Friday in one of Iran's boldest statements yet.
China has also announced that representatives of the five permanent Security Council members, plus Germany, would meet on Tuesday in Moscow to discuss the crisis.