As a half-dozen of Iran's most advanced ballistic missiles roll by, at the climax of a military parade this week, the anti-US rhetoric appears unchanged.
"We will crush America under our feet," the painted lettering reads, on the Shahab-3 missile - a rocket with a 1,000-mile range that the Islamic Republic vows can "hit the heart of the enemy" US-ally Israel.
But behind the scenes, analysts say that the US occupation of Iraq - and continued instability there - is prompting both Tehran and Washington to reappraise their archenemy status, and find a number of pragmatic reasons not to antagonize each other.
"The Iranians are up for [a deal], to a point. They don't want a fight," says Ali Ansari, at the Royal Institute of International Affairs in London. "On the US side, they don't want to make any more enemies in the region. If they antagonize [Iran], hard-liners could whip up real trouble."
A blossoming détente is hardly possible, as questions persist about Iran's nuclear program and the presence of several Al Qaeda chiefs here. Iran is also worried about the US military presence on three borders, and that the Islamic Republic - after Afghanistan and Iraq - could be "next."
But a visit to Tehran a week ago by Jordan's King Abdullah II, followed by his trip to Washington to meet President George Bush at Camp David, may have been a key link.
"[Abdullah] received some new analysis about the region from President [Mohammad] Khatami and Foreign Minister [Kamal] Kharrazi, and transferred that analysis to the US," says Abbas Maleki, Iran's former deputy foreign minister who now runs a Caspian studies institute in Tehran.
Indeed, before visiting Bush, the Jordanian monarch told The Washington Post that he had found "common ground" between US and Iranian security interests, including a mutual fear of the threat from Al Qaeda and Sunni Muslim extremists.
The king said there is "common grounds for a dialogue," between the US and Iran, adding that a shift in policy is "a decision that [Bush is] going to make."
Though Iran remains on Bush's "axis of evil" list, strategic concerns may be causing a tactical thaw.
"We now have more border with the US [occupied countries] than Canada, and we hope this makes the US familiar with realities in the region," says Mr. Maleki. As the US military gets more deeply embroiled in postwar Iraq, anti-Iran rhetoric has tapered off, he says, "because they reached the conclusion they can't fight on different fronts."
Western diplomats and analysts in Tehran dismiss US claims from Baghdad that Iran is systematically seeking to undermine the Iraq occupation, saying that Iran also has a stake in stability there.
"Iran has no interest in creating, or being linked to, any kind of problems the Americans are facing in Iraq," says a Western diplomat. "They understand the price to be paid for doing that.
"If in some circles, [Iranians] are happy when Americans are killed in Iraq, the government and many conservatives don't share that joy," the diplomat adds. "Every setback for the Americans is bad news, because it lengthens the occupation and delays the moment when the Shiite [majority] will take control."
"They didn't raise a finger, and Saddam Hussein is gone. They didn't raise a finger, and the Americans are in trouble without them," notes another, senior Western diplomat. "The principle is not to act. I'm not saying they don't do anything [against the US in Iraq], but the role is marginal."
Secret back-channel meetings are known to have been held during the past two years. And despite the show of force on Monday - the largest parade of its kind in Iran for years, with everything on display from tanks and drones to heavy artillery - Iranian leaders sought to strike a balance.
"Even if we don't give a pretext to the enemy, they will find one," Khatami told the thousands of troops. "Despite all the pressure from our enemies, we will pursue our policy of détente, but we will also insist on becoming stronger."
The influential hard-line Revolutionary Guard commander, Brig. Gen. Yahya Rahim-Safavi, said the "powerful" display showed that Iran is "ready to help establish peace in the region."
Those looking for a shaft of light on US-Iran ties, point to an article several months ago by Ali Akbar Hashemi Rafsanjani, the powerful chair of the Expediency Council. He described ways to solve the problem, that included intervention by Iran's supreme religious leader - who has final say on all foreign policy issues - a referendum, or even a vote in parliament.
Interest in better bilateral relations has already filtered down to the street. Iranians are obsessed, pro and con, with America.
"The situation in Iraq has caused [Iranian leaders] to change their mind. They know there is no other way than friendship with the US. It's the only way to save Iran and the Iranians," says Kimia, a recent professional-school graduate. "I'm not a pro-American woman ... and people are not impressed with the Afghan and Iraqi examples. But people are tired and want to be free, and think [US ties] could be a good way."
Such high regard has led some here to expect US intervention, following Bush's encouragement of antiregime demonstrations last June. Upon hearing an American accent, Iranians often ask: "America good! When will Bush come?"
But anti-US actions often match the flag-burning public rhetoric. One example is the case of the Abbas Abdi - one of the students who took over the US embassy more than 20 years ago, who has since become a staunch reformer. Mr. Abdi was jailed last November, charged with "providing information to the enemies of the Islamic regime" for conducting a poll that found 75 percent of Iranians favoring renewed ties with the US.
And there are still key obstacles that threaten any possibility of US-Iran warming. One is the officially confirmed presence in Iran of a handful of top Al Qaeda leaders, though their circumstances - are they being hosted or detained and by whom? - are unclear, diplomats say.
Among them are believed to be Osama bin Laden's son, Saad, the movement's No. 2 and No. 3, Ayman al-Zawahiri and Saif al-Adel, and spokesman Sulaiman Abu Ghaith.
Considering the long-standing enmity between Al Qaeda and Iran, analysts here say that the Al Qaeda presence is a high-stakes bargaining chip.
"[Iran] feels it has a hot potato, and doesn't know what to do with it," says a senior Western diplomat. "They don't like Al Qaeda, and had less contact with Al Qaeda than even the CIA did before Sept. 11."
Iran initially denied the presence of any Al Qaeda members, then extradited a handful to Saudi Arabia early last year. Iran has reportedly told the US and other countries that Al Qaeda leaders in Iran have now been detained, and are not allowed to communicate.
"The really difficult moment will be if there is a major attack on a Western target or America," says a Western diplomat. "If something is remotely tied to Qaeda operating in Iran - something that could have been prevented, if Iran had handled it right - I would hate to see the reaction from Washington."
And that possibility feeds skeptics in Tehran. "Because of the open hostility of Bush to Iran, the basis for those who want [US-Iran] relations is very weak," says Taha Hashemi, editor of the conservative Entekhab newspaper. "But as we say in Persian, there are many hopes in disappointment."