Editor's note: Vali Nasr is a professor of international politics at the Fletcher School of Law and Diplomacy at Tufts University and senior fellow at Brookings Institution. He is the author of several books including, "The Shia Revival" and "Democracy in Iran."
(CNN) -- The U.S. government's newly revealed charges that Iran planned to assassinate Saudi Arabia's ambassador to the United States is nothing short of mind-boggling.
It is difficult to see what Iran would have gained by simultaneously escalating tensions with its main regional rival and also ratcheting up tensions with the United States. If true, this plot shows a monumental lapse in judgment on Tehran's part, an audacious and reckless adventurism that will go down as the clerical regime's colossal mistake that will weaken its hand internationally and even unravel its grip on power -- or there is something the Iranian regime knows and has put its bets on that no one else is aware of.
We will not know the answer any time soon. What is certain at this juncture is that U.S.-Iran relations have entered a new and more dangerous phase, and how Iran will play its part in the confrontations that are bound to follow not only will be decisive for Middle East security but also for the future of the Islamic republic.
Saudi Arabia and Iran have not enjoyed good relations for three decades. Riyadh sees the Islamic republic as a threat to its stability and that of the Persian Gulf, and as a rival for leadership of the Islamic world. A majority of Iranians are Shiites, the smaller of Islam's two main sects. Saudi Arabia sees itself as a Sunni power, and as such, the leader of Muslim world. The two have repeatedly clashed over who speaks for Islam and how to define the Muslim world's attitude toward politics and relations with the West.
There was a brief thaw in their relations in the 1990s when revolutionary fervor in Iran subsided and the Iranian government took measured steps toward reform. But reform proved to be ephemeral, and with the election of Mahmoud Ahmadinejad to the presidency, Iran presented a new hard-line face to the world. And with that relations between Iran and Saudi Arabia grew frosty.
The U.S. invasion of Iraq has proved to be as much about Iran and Saudi Arabia on a collision course as it was about introducing democracy to the Middle East. Iraq started a Cold War between the two that defines the region's dynamic. The Iraq war transferred power in that country from its ruling Sunni minority to its disenfranchised Shiite majority. With Shiites in power, Iraq moved closer to Iran. The sectarian conflict that unfolded in Iran in 2006-'07 brought to light a new fault line in regional politics, one that reflected the ongoing Saudi-Iranian rivalry. Saudis supported the Sunnis of Iraq and Iran its Shiites.
What started in Iraq then continued elsewhere in the region. There are Sunni-Shiite competitions for power in Lebanon, Syria, Bahrain, Yemen and Pakistan. In the past five years, each of these competitions for power has also involved Iran and Saudi Arabia, and each instance has further aggravated relations between the two.
Most notably, as the Arab Spring spread to the Persian Gulf, Bahrain's majority Shiite population demanded greater say in government. That threatened Bahrain's Sunni monarchy. Saudi Arabia saw this as a repetition of Iraq: pro-Iran Shiites vanquishing a Sunni regime friendly to Saudi Arabia. Riyadh reacted viscerally to this threat by encouraging Bahrain's monarchy to crack down on protesters.
Bahrain, however, was a dress rehearsal for Syria, where a minority sect of Islam that is closely affiliated with Shiism rules over a majority Sunni population, and where the ruling regime is Iran's closest ally in the Arab world. In Syria, Iran supports the Bashar al-Assad regime while Saudi sympathies lies with the opposition. The Shiite-Sunni, and by turn Iranian-Saudi, rivalry that erupted during the Iraq war has reached fever pitch with the Arab Spring.
It is easy to conclude that Iran saw the assassination of the Saudi ambassador to Washington as a shot across Saudi Arabia's bow. But the choice of location has made this all about U.S.-Iran relations.
Washington and Tehran are locked in an impasse over Iran's nuclear program. Washington wants Iran to scrap the program, and Iran refuses to compromise on what it sees at its right to develop nuclear technology under international agreements. The backdrop to all this is ongoing low-level clashes between American forces and Iranian proxies in Iraq and Afghanistan.
Iran's Quds Force -- also believed to be behind the Washington plot -- has been America's nemesis across the Middle East, arming Hezbollah in Lebanon and Shiite militias in Iraq, and meddling in Afghanistan. U.S. troops in the Persian Gulf sit in bases barely 100 kilometers from the Iranian shore. Iran is the only country in the region that the United States is in conflict with in multiple military arenas.
Last month, Adm. Mike Mullen, then-chairman of Joints Chief of Staff, suggested that U.S. and Iranian navies establish a hotline to reduce the possibility of inadvertent escalation of tensions into conflict. Iran seems to have been seeking exactly such an escalation.
It is possible that Iran thought its fingerprints would not be found in the murder of the ambassador. Alternately, it may be that Iran welcomes a direct confrontation with the United States, possibly to divert attention from political and economic woes at home, and to rally the Middle East against the United States.
That would be worrisome. Conflict with the United States is usually deterrence to aggression. To manage the actions of a country that actually seeks conflict, the United States has to adopt a very different tack.
Washington is bound to react to this incident with more economic sanctions and perhaps new punitive measures against the Iranian government. But the Iranian challenge has now evolved into something altogether different, and to address this challenge, the United States has to rally the international community.
An important first step is to make public all the details of this plot. In the Middle East in particular, it is only with clarity of facts that the United States can make a convincing case for why the Iran's anti-American posture and violent tactics is not heroic bravado deserving of accolade, but a cynical gamble that endangers the whole region.
The opinions expressed in this commentary are solely those of Vali Nasr.