The United States accused Iran of planning to assassinate the Saudi Arabian ambassador to the country on Tuesday. A man linked to Iran’s security services was arrested in the United States last month while another man suspected to be involved in the plot was believed to be in Iran.

Iran denied the allegation. The chairman of the Iranian parliament suggested that the United States wanted “to divert attention from problems it faces in the Middle East, but the Americans cannot stop the wave of Islamic awakening by using such excuses,” he said.

Target of the alleged plot was Adel al-Jubeir who has been Saudi ambassador to the United States since 2007. Relations between Iran and Saudi Arabia have deteriorated in recent years. With Egypt and Iraq both weakened since the dictatorships were toppled there, Saudi Arabia is the only Sunni power in the region still standing. But its influence is eroding. The Saudi backed government of Lebanon was undermined by Iranian ally Hezbollah earlier this year. This year’s political unrest in Bahrain, as far as the Saudis are concerned, is part of an Iranian conspiracy against their kingdom.

The tiny Persian Gulf state is ruled by a Sunni monarchy but home to a Shia majority. Iran expressed support for the Shia uprising but there was no evidence that it backed it with anything but rhetoric.

Saudi Arabia nevertheless intervened with other Gulf Cooperation Council monarchies to quell the protests in Bahrain. Some 2,000 Saudi and emirate forces were deployed to suppress the demonstrations and combat suspected Iranian encroachment on the Arabian Peninsula.

The suspected Iranian assassination plot of the Saudi ambassador to the United States may have been designed as retaliation for March’s military intervention but to stage such a countermeasure on American soil would have been very risky.

If true, it would represent a radical departure from the proxy war that Iran has waged against Israel and, by extension, the United States in previous years. If the plot were carried out successfully and Iranian involvement uncovered, retaliation could have been devastating.

Republican congressman Peter King, who chairs the House Committee on Homeland Security, told CNN on Tuesday that the plot was tantamount to “an act of war” and said that sanctions weren’t enough anymore. “We can’t allow this to go without a strong reaction by us.” Imagine the response if the attack hadn’t been thwarted.

Iran hasn’t built a nuclear weapon yet with which to deter an American retaliatory strike. Staging a terrorist attack on American territory, even when targeting a foreign diplomat, could have born enormous repercussions for Iran which no rational government would be willing to bear.

Nevertheless, it seems likely that the Iranian leadership was informed of the planned attack, if it didn’t order it.

The United States suspect involvement of the Quds Force of the Iranian Revolutionary Guard which is charged with “exporting” the Islamic revolution and answers directly to the Ayatollah Ali Khamenei. Its members liaison between Tehran and militant Islamist movements like Hezbollah which has been responsible for terrorist attacks in Israel and Lebanon. The organization was blamed by the United States for stirring sectarian unrest in Iraq after Western powers invaded there in 2003.

Iran’s current defense minister, Ahmad Vahidi, a former Revolutionary Guards commander, belonged to the Quds and cultivated close ties with Al Qaeda’s Ayman al-Zawahiri, formerly Osama bin Laden’s lieutenant who assumed control of the terrorist network after his boss’ assassination in May of this year. President Mahmoud Ahmadinejad was also once an officer in the Guards and has consistency elevated its officials’ role in the Iranian government.

Given this, it’s difficult to imagine that the upper echelons of the Iranian government weren’t either aware of or involved in the planned attack — if indeed such an attack was intended to be carried out.