A Bahraini woman holds a poster of prominent Shiite Muslim cleric Nimr al-Nimr during clashes with police after a protest against his execution in the Bahraini capital, Manama, on Jan. 4, 2015. (Mohammed Al-Shaikh/AFP/Getty Images)

Saudi Arabia said Tuesday that its feud with Iran would not interfere with Syrian peace talks scheduled to begin later this month, signaling an easing of the tensions that erupted after the kingdom’s execution of a prominent Shiite cleric.

Kuwait meanwhile joined the list of Saudi Arabia’s Sunni-led allies to cut or downgrade ties with Iran, saying that it has recalled its ambassador to Tehran in solidarity with the kingdom after Riyadh’s severance of diplomatic relations with Iran on Sunday.

The rift is the most serious between the region’s rival Sunni and Shiite powers since Saudi Arabia and Iran last cut ties in the 1980s over tensions stemming from the Iran-Iraq war, and it raised the specter of a wider conflict in a region already convulsed by several wars.

[The seven most important moments of the Saudi-Iranian rivalry]

Among them is the conflict in Syria, which has raged unchecked for nearly five years and only now has emerged as a key priority for the Obama administration’s foreign policy team. Bringing peace to Syria will be the administration’s “foremost challenge” for the year ahead, Secretary of State John F. Kerry said in an opinion piece marking the new year.

At the White House, press secretary Josh Earnest says the United States is calling for restraint amid Saudi-Iranian tensions over Saudi Arabia’s execution of a prominent Shiite cleric. (Reuters)

Central to the challenge is the effort to reconvene peace talks in Geneva that failed spectacularly two years ago after less than a month. The new rift between Saudi Arabia and Iran had imperiled those talks, which could not proceed without the support of both countries, as sponsors of rival factions in the war in Syria.

Kerry spent most of the past two days on the telephone with Saudi and Iranian leaders as well as with officials of other coalition countries in the region “to encourage de-escalation,” according to Brett McGurk, President Obama’s special envoy to the coalition against the Islamic State group.

“One of the key things on Kerry’s mind is not letting the Vienna process stall or fall backward,” said State Department spokesman John Kirby, referring to a statement in Vienna last year proposing ways to end the Syrian war that was agreed to by Saudi Arabia and Iran.

After meeting with Saudi Foreign Minister Adel al-Jubeir in Riyadh on Tuesday, the U.N. special envoy for Syria said he had been assured that Saudi Arabia would not allow the latest falling-out with Iran to interfere with the talks.

“There is a clear determination on the Saudi side that the current regional tensions will not have any negative impact on the Vienna momentum and on the continuation of the political process that the U.N, together with the International Syria Support Group, intend to start in Geneva soon,” special envoy Staffan de Mistura said after the meeting, according to a U.N. statement.

Saudi Arabia affirmed those sentiments, with the official Saudi press agency saying that the spat with Iran “would not affect” the peace talks “negatively.”

“We will continue working with you and the international community in order to reach a political solution for the Syrian crisis,” the agency quoted Jubeir as saying.

Saudi Arabia and Iran have harbored long-running suspicions and outright hostility toward each other. Here’s why. (The Washington Post)

Jubeir also told de Mistura that Saudi Arabia would continue to provide “military, political and economic support to the Syrian people,” a reference to Saudi Arabia’s backing of the opposition to Syrian President Bashar al-Assad’s government.

It remains unclear whether Iran will remain committed to the talks in light of the rupture. De Mistura is due to visit Iran for a previously scheduled meeting at the weekend, according to Iranian media reports.

But the State Department welcomed expressions of regret by Iran for the ransacking and burning of the Saudi Embassy contained in a letter to the United Nations from Iranian officials. A senior Obama administration official also noted that while Bahrain and Sudan had followed Saudi Arabia’s lead in severing relations with Iran, Kuwait and the United Arab Emirates had only downgraded them.

The official spoke on the condition of anonymity to discuss the sensitive rift, which has presented the Obama administration with a dilemma: As it is seeking improved relations with Iran, a long-standing U.S. enemy, a major rupture has taken place between Iran and its longtime regional ally Saudi Arabia.

The crisis erupted over the weekend when Saudi Arabia executed a prominent Shiite cleric, Nimr Baqr al-Nimr, triggering angry demonstrations in Tehran during which the Saudi Embassy was ransacked and burned.

[Who is the Saudi cleric whose execution caused the Riyadh-Tehran blowup?]

The crisis drew worldwide expressions of alarm and appeals for restraint, amid growing concerns about the potential for conflict in an already volatile region that controls access to a third of the world’s oil supply.

DeYoung reported from Washington. Brian Murphy in Washington contributed to this report.

Read more:

How Saudi Arabia and the Islamic State find common ground in beheadings

The seven most important moments of the Saudi-Iranian rivalry

Who is the Saudi cleric whose death caused the Riyadh-Tehran blowup?

7 remarkable insults in the Iran-Saudi Arabia war of words