The sudden escalation of tensions between the United States and Iran threatens to reignite old feuds and exacerbate new ones across a region already dangerously destabilized by the tumult of the Arab Spring.

From Tunisia to Egypt, Yemen, Libya, Bahrain and Syria, the popular revolts underway since January have drawn new battle lines in a part of the world long associated with confrontation, pitting the ruled against their rulers and raising hopes that the struggle for greater freedoms by ordinary people will give birth to a new, improved Middle East.

The announcement of the alleged Iranian assassination plot against the Saudi Arabian ambassador in Washington serves as a stark reminder that the old Middle East — the one of geopolitical rivalries, conspiracies and the ancient Sunni-Shiite divide — remains very much alive.

And now, as the uncertainties of the new Middle East collide with the realities of the old, the outcome could be explosive, many fear.

“Somebody in Iran will have to pay the price,” Saudi Prince Turki al-Faisal said at an oil conference in London on Wednesday, in a comment that underscored the depth of Saudi anger at the alleged attempt on the life of one of Saudi King Abdullah’s most trusted confidants.

“I can see a crisis coming. I can see a wider confrontation,” said Jamal Khashoggi, a prominent Saudi journalist who identified Syria as the most likely venue. “But on what scale and how it will happen, I don’t know.”

Countries focused inward

The relatively measured response of Iran, which hotly denied the allegations but did not threaten retaliation, as well as the continued preoccupation of most regional leaders with their own domestic problems, suggest no immediate danger of military escalation.

“Iran won’t respond because it doesn’t need to, and the Saudis are not in a position to retaliate because they have a lot of problems of their own,” said Oussama Safa, an independent political analyst in Beirut. “This is definitely bound to blow up at some point, but right now the region is more distracted by problems of the Arab Spring.”

On the streets of Beirut, the venue for one of the most recent confrontations between Iran’s Shiite allies and Sunnis supported by the United States and Saudi Arabia, people were dismissive of the alleged plot.

“This is another game being played by America and Iran,” said Jamal Baghdadi, who sells tourist knickknacks in downtown Beirut. He said he was confident there would be no replay of the conflict that began in 2006 with an Israeli onslaught aimed at crushing Iran’s Shiite ally Hezbollah and ended with Hezbollah seizing control of mostly Sunni West Beirut in 2008 — one of the more overt examples of the kind of proxy confrontation that some fear could erupt anew.

The popular rebellions of the past 10 months had detracted attention from the very real threat posed to the region’s stability by Iran and its nuclear program, said Salman Shaikh, director of the Brookings Doha Center in Qatar. The plot allegations promise to restore that issue, which dominated the region’s discourse for much of the past decade, to center stage, along with the broader struggle for supremacy in the region between Iran and its mostly Shiite allies in Iraq, Syria and Lebanon, and the United States, through its relationships with Sunni Saudi Arabia and Israel.

“This takes us back to an older period and an older set of rivalries which are part of the competition and struggle to reshape the region,” he said. “Most people are shrugging their shoulders or laughing about this plot, but the region is in a dizzying phase and these old and new rivalries create more confusion . . . and the wire is now more taut.”

Though outright war seems unlikely, the potential for a misunderstanding has risen sharply in any one of a number of flash points, from the busy shipping lanes of the Persian Gulf, where U.S. and Iranian warships cross paths on a daily basis, to any one of the many countries whose Sunni-Shiite divide risks being aggravated by the renewed tensions.

They include Yemen, Lebanon and Bahrain, where Saudi troops helped the minority Sunni government crush a mostly Shiite revolt in March, as well as Saudi Arabia, which last week indirectly accused Iran of fomenting anti-government demonstrations among Shiites in the east of the country.

The ongoing bloodshed in Iraq, where Shiites backed by Iran fought a bloody war for dominance over minority Sunnis in the wake of the U.S.-led invasion, could also escalate as regional powers compete to fill the vacuum left by departing U.S. troops.

‘The next battleground’

Nowhere, however, is the fallout more likely to be felt than in Syria, whose uprising has emerged as the most complex and potentially combustible of the Arab revolts, with the country’s volatile sectarian divide and its strategic location.

On Wednesday, tens of thousands of Syrians swarmed a central square in Damascus in a show of support for President Bashar al-Assad that eclipsed the size of any anti-government demonstration so far in the capital, underscoring that the battle for control of the country is still far from resolved.

The majority-Sunni country, governed by a minority Shiite sect, has long served as a conduit for Iran’s expansionist ambitions in the Arab world, and if Saudi Arabia were to decide to retaliate, it would most likely be there, said Khashoggi, the Saudi journalist.

“Syria is the next battleground,” he predicted. “Many Saudi Arabians feel there is an extended Iranian hand in Syria, and Syria is not the Iranian domain. They say Syria is our domain, and that a mistake of history put a minority in charge.

“But it is our territory, and this is our opportunity to correct this mistake of history.”