If the rival factions that dominate Iranian politics have drawn one common lesson from the war in Iraq, it is not to underestimate Washington's resolve in confronting what it considers "rogue states" in the region.
The Iranian establishment vowed this week to defend Syria against U.S. threats by using all nonmilitary means at its disposal. But the moderate government of President Mohammad Khatami and officials within Iran's hard-line state institutions are stepping cautiously in determining how much support they will give Syria.
With the Bush administration already warning Syria against harboring terrorists and weapons of mass destruction -- allegations that mirror long-standing U.S. complaints against Iran -- officials here are hurriedly cobbling together a diplomatic contingency plan should Washington move to isolate or otherwise pressure Iran.
Many officials say it is only a matter of time before the Bush administration renews its criticism of Tehran, particularly the charge that it seeks to build nuclear weapons. Some believe Iran must revamp its diplomacy to discourage U.S. military action.
Washington's rapid shift of attention to Syria has alarmed Iranian officials, who had hoped for a drawn-out war in Iraq that would have distracted the United States.
"A tired, drained America would've been much better for us," one senior official remarked.
The most visible indication of Iran's anxiety was the suggestion by former President Hashemi Rafsanjani shortly after the fall of Baghdad that Tehran and Washington resume ties. "Our ideology is flexible," Rafsanjani said.
But reformist and conservative circles alike criticized Rafsanjani, saying that reaching out so publicly was a tactical error. "The timing was all wrong," said Taha Hashemi, editor of conservative newspaper Entekhab. "It gave the United States the impression that Iran is terrified."
There is a consensus that the time for friendly signals between old enemies is over and that Iran must take practical steps to defuse what is viewed as an imminent threat.
"Our first priority is a diplomacy of deterrence," Hashemi said. "We need to take away any pretexts" for U.S. threats.
Tehran hopes the European Union, especially Britain, can dissuade Washington from dealing harshly with Iran. But before the EU would lobby on Iran's behalf, it is believed, the country would have to make policy changes such as improving human rights, vowing not to manufacture nuclear weapons, and toning down rhetoric against Israel.
But reformers worry that these steps would be insufficient to alleviate Washington's concerns. For example, Western diplomats point out that Iran still refuses to acknowledge that elements inside the country are harboring Al Qaeda members who fled over the border from Afghanistan.
Washington wants Iran to drop its call for the destruction of Israel; cut funding to violent, pro-Palestinian groups such as Hamas and Islamic Jihad; and settle for a more rudimentary nuclear energy program that would not easily lend itself to weapons production.
But taking any of these steps could bring domestic repercussions. "Hard-liners can't back down on these issues," said Hadi Semati, a political science professor and advisor to Khatami.
Militant support for Palestinians is a central pillar of the revolutionary ideology still clung to by many powerful, hard-line religious leaders. A more moderate stance on a cause so central to the Islamic world, they believe, would undermine the regime's religious legitimacy.
"Until these internal differences are resolved, Iran can't deal with external threats," said a Western diplomat in Tehran.
Reformers have stepped up their warning that the Islamic regime risks losing popular support if it continues obstructing liberal changes.
As one prominent reformist put it: "We want them to ... take this lesson from Iraq: This is the fate of dictatorships."