Secretary of State John Kerry and others in the Obama administration have issued statements urging leaders across the region to take steps to "calm tensions." | Getty White House goes into damage control on Syria peace talks The clash between Saudi Arabia and Iran is threatening to unravel the progress made in the effort to end Syria's civil war.

An escalating dispute between Saudi Arabia and Iran is threatening to derail President Barack Obama’s efforts to bring an end to the civil war in Syria while also undermining the U.S.-led fight against the Islamic State terrorist network.

Saudi Arabia cut off diplomatic ties to Iran over the weekend after Iranian protesters — angry over Riyadh’s execution of a prominent Shiite cleric — attacked the Saudi embassy in Tehran. On Monday, Bahrain and Sudan also announced they were severing diplomatic relations with Iran, while the United Arab Emirates said it was downgrading ties. Saudi Arabia also moved to halt commercial ties with and stop flights to and from Iran, Reuters reported, while the events jolted oil markets.


Meanwhile, Staffan de Mistura, the United Nations envoy tasked with trying to end the Syrian conflict, was heading to the Middle East to persuade the Iranians and Saudis not to scuttle that process.

“You have to assume that neither side wants it to escalate. But it’s the sort of thing that can get out of hand,” said Philip Gordon, a former top Obama aide deeply involved in Middle East affairs.

Obama aides scrambled to respond to the sudden turn of events, which follow years of growing sectarian and nationalist tension between Sunni-majority Saudi Arabia and Shiite-majority Iran. Secretary of State John Kerry called Iranian Foreign Minister Mohammad Javad Zarif on Sunday, and according to the Saudi Press Agency, Kerry called Saudi Deputy Crown Prince Mohammad bin Salman Al Saud on Monday. White House spokesman Josh Earnest, in unusually even-handed terms, chided both Iran and Saudi Arabia and urged the two parties to calm tensions for their own sake, although State Department spokesman John Kirby stressed that the U.S. did not plan to insert itself as a mediator.

The flaring conflict between the two countries is a setback for Obama’s diplomacy and foreign policy legacy, which has been badly damaged by the five-year-old civil war in Syria, where 250,000 people have been killed, and the rise of the Islamic State terrorist group, also known as ISIS or ISIL, which has seized territory in Syria and Iraq and inspired the recent attacks in Paris and California. The Saudi-Iran spat also comes as the U.S. and its allies are making some progress on both those fronts as well as in Yemen, where Saudi forces are battling Iranian-backed rebels.

A peace process was launched late last year for Syria, and the U.N. was due to bring together the warring parties for talks in Geneva on Jan. 25. Iran, which has backed Syrian President Bashar Assad, and Saudi Arabia, which has supported rebels trying to oust him, have both been involved in the diplomatic efforts.

Their willingness to be in the same room was considered groundbreaking. Both are regional powers vying for influence throughout the Middle East and on the world’s oil markets. Although both are Islamist states, they adhere to rival branches of Islam. Saudi Arabia also is an Arab nation, while Iran’s population is majority Persian.

Iran’s growing influence in countries such as Lebanon, Yemen and Syria has deeply concerned the Saudis, who feel the United States, despite its longstanding enmity toward Iran, doesn’t do enough to rein it in. The U.S. decision to pursue a nuclear deal with Tehran further fed Saudi fears of a potential Washington-Tehran rapprochement.

The Saudi decision to execute Shiite cleric Nimr al-Nimr is just the latest example of Riyadh’s willingness to confront Iran without waiting for permission from the U.S. Earnest confirmed Monday that U.S. officials had urged the Saudis to think twice about carrying out the death sentences, especially that of al-Nimr, precisely because it could lead to a backlash.

“Unfortunately, the concerns that we expressed to the Saudis have precipitated the kinds of consequences that we were concerned about,” Earnest said.

The new Saudi-Iran dispute “sort of sends you back to the drawing board” on Syria, Gordon said, especially because the Vienna process was premised on the idea that the Saudis and the Iranians could compromise.

“On a recent trip to the kingdom I was struck by the degree to which Iran was the overwhelming national security concern and threat perceived by the Saudis, even ahead of ISIS, Assad, the Muslim Brotherhood and other adversaries,” Gordon said. “It's impossible to make progress in Syria and Yemen and elsewhere so long as this rivalry goes on.”

Earnest suggested that the Saudis and the Iranians could be persuaded to stay involved in the Syria peace effort if only because the chaos in Syria threatens their own stability. “The pursuit of this ultimate goal is so clearly within their own direct interest. We’re hopeful they will continue to engage, but ultimately that will be up to them,” the spokesman said.

Earnest made it clear the U.S. is unhappy with both the Saudi moves and the Iranian reaction, and he even made a point of noting that the administration has concerns about the human rights situation in Saudi Arabia. The comments were striking because while the U.S. does not have formal diplomatic ties with Iran and has historically been willing to criticize Tehran quite openly, U.S. officials are normally very careful about condemning actions by the Saudis, who are considered a crucial ally.

The U.S. has cautiously backed Saudi forces in Yemen, where Iran-backed Houthi rebels ousted the government supported by Riyadh and where months of fighting have resulted in thousands of civilian casualties. A fragile peace process in the works there also seems destined for the dumps thanks to this weekend’s events.

The Saudis and the Iranians both despise the Islamic State, and Obama aides consider the terrorist group the top threat in the region. But there is a recognition that the jihadists will continue to thrive so long as the civil war in Syria goes on, making this weekend’s events an even bigger problem. The Islamic State and Al Qaeda have each managed to make gains in Yemen as a result of the Saudi-Iran proxy fight there.

Saudi authorities executed al-Nimr, a prominent critic of the Saudi royal family, alongside 46 other people, most of whom were alleged Sunni extremist militants. The mass execution in a country whose opaque justice system is based on a strict version of Islamic law drew condemnations from human rights activists.

“The Jan. 2 executions, in 12 different locations, were reported to have taken place by firing squad or beheading,” wrote Simon Henderson, an analyst with the Washington Institute for Near East Policy. “Whatever the gruesome details, the executions undermined Saudi Arabia’s attempts internationally to distinguish its methods of punishment from those of the Islamic State. While the kingdom is spending tens of millions in fees to Western investment banks and management consultancies for advice on how to restructure its economy, it appears at best tone-deaf to negative impressions of some of the ways Islam is practiced in the kingdom.”

Saeed al-Wahabi, a Saudi analyst, said he was surprised that Saudi-Iranian diplomatic relations were cut off — “It's a big thing” — but said in his opinion the mass executions’ “secondary goal” was to send messages to Washington and Tehran, while “the primary one is that Riyadh is serious about countering terrorism and securing its territories.”

Iran, which considers itself the leading center for the world’s Shiite Muslims, condemned the execution of Nimr, but the Saudis allege it was slow to call off protesters who attacked the Saudi Embassy in Tehran and the Saudi consulate in the city of Mashhad. According to the Saudi Foreign Ministry, the protests appeared highly organized, with demonstrators participating in shifts and Iranian guards looking the other way at the ensuing destruction. Saudi officials said their requests for protection from Iran’s Foreign Ministry were ignored.

As the war of words between the two sides grew, Saudi officials were particularly harsh, repeatedly calling Iran a sponsor of terrorism.

“We are determined not to allow Iran to undermine our security. We are determined not to let Iran mobilize or create or establish terrorist cells in our country or in the countries of our allies. We will push back against Iran’s attempts to do so,” Saudi Foreign Minister Adel Al-Jubeir said.

Iranian Supreme Leader Ayatollah Ali Khamenei used his Twitter account throughout the weekend to snipe at the Saudis, at one point tweeting: “Surely, martyr #SheikhNimr will be graced by God & no doubt Divine revenge will seize oppressors who killed him & it is the point of relief.”

By mid-day Monday, there were some signs of conciliation amid growing international pressure on Tehran and Riyadh. The Associated Press reported that in a letter to U.N. Secretary General Ban Ki-moon, Iran’s U.N. envoy expressed “regret” over the attacks on Saudi diplomatic facilities and noted that Iran already had arrested dozens of people and was seeking other potential perpetrators.