Iraqi police officers stand guard holding posters of prominent Shiite cleric Sheik Nimr Baqr al-Nimr, who was executed by Saudi Arabia, during a demonstration in Baghdad on Monday. (Ahmad al-Rubaye/AFP/Getty Images)

The Obama administration’s cautious approach to the latest eruption in tensions between two major Middle Eastern powers reflects a reluctance to take sides in a dispute where it believes both are at fault, and a sense that a strong U.S. intervention would have little effect and might make things worse.

Secretary of State John F. Kerry spoke by telephone Monday with Saudi Arabia’s deputy crown prince and defense minister, Mohammed bin Salman, and with Foreign Minister Adel al-Jubeir, following a call Sunday to Iranian Foreign Minister Mohammad Javad Zarif, senior administration officials said.

Kerry appealed to both sides to deescalate their dispute — which was sparked over the weekend when the Saudis executed a prominent Shiite cleric, mobs attacked the Saudi Embassy in Tehran in retaliation, and Riyadh then severed diplomatic relations with Iran — before it goes any further. But “ultimately these are issues that these countries have to work out for themselves,” State Department spokesman John Kirby said.

“If you’re asking if we’re trying to be a mediator in all this, the answer is no,” Kirby told reporters.

At the White House, press secretary Josh Earnest says the U.S. is calling for restraint in Saudi-Iranian tensions over the killing of a prominent Shiite cleric. (Reuters)

At the White House, press secretary Josh Earnest emphasized the same message. “I guess the point is there’s plenty of blame to go around, and what we would like to see is all sides begin to take the kinds of steps that will deescalate and not inflame the tensions that are obviously pretty raw right now.”

The administration’s attempt at balance illustrates the thin line the United States walks in maintaining a strong relationship with Saudi Arabia, a major oil producer and regional power whose conservative Sunni majority has long been seen as part of the problem as well as the solution in countering terrorist groups such as al-Qaeda and the Islamic State.

The call for both sides to calm down brought criticism from at least two Republican presidential candidates, Ben Carson and Carly Fiorina. Both called Saudi Arabia a strong U.S. ally that should be supported, and they repeated their criticism of the Iran nuclear deal as a partial explanation for Saudi actions.

But administration statements, if anything, seemed more critical of the Saudis for provoking a conflict that could undermine another top U.S. priority in the region: negotiations between the Syrian opposition and the government of President Bashar al-Assad to end that country’s civil war.

Kerry succeeded last month in persuading Jubeir, whose Sunni government backs the opposition, and Zarif, whose Shiite government supports Assad, to sit down together for the first time as part of an international effort to promote a negotiated end to the Syrian civil war. Either side could now upend the talks, scheduled to begin Jan. 25.

“We don’t want to see any progress that has been made or may be made [on Syria] affected by this,” Kirby said. “We still hope and expect that meetings between the opposition groups and the [Assad] regime can happen this month as planned.”

While U.S. officials and even the Russian government — allied with Iran in Syria — condemned the sacking of the Saudi Embassy in Tehran, most attention was focused on Saudi Arabia.

Administration officials and Middle East experts attributed the execution of Saudi Shiite leader Sheik Nimr Baqr al-Nimr primarily to domestic concerns stemming from the royal family’s perceived need to appease influential Sunni clerics in that country.

“If you’re sitting in Riyadh, the confluence of external forces and domestic pressures tend to blur,” said Frederic Wehrey, a senior associate in the Middle East program at the Carnegie Endowment for International Peace. “They look beyond their borders and see perhaps the balance of power tilting toward Iran. The flip side” is the domestic pressure they face from their Sunni constituents.

“The best way to bind them to the royal family is to play that Iran card. . . . They can’t push too hard and antagonize these clerics,” he said.

Officials said the Saudis informed the administration several weeks ago of a pending mass execution of dozens of alleged terrorists. The vast majority were al-Qaeda-related Sunnis, and Wehrey speculated that Saudi leaders figured they would “take care of some Shia while we’re at it to try to balance the equation.”

The United States has long joined international human rights organizations and other Western governments in criticizing Saudi human rights abuses and the country’s opaque judicial system. Nimr had become a particular cause celebre among human rights campaigners, and Iran had repeatedly demanded his release.

In this case, U.S. officials said they privately pressed the Saudis to leave Nimr, convicted two years ago of promoting terrorism because of his support for dissidents among the kingdom’s Shiite minority, out of their execution plans. Nimr’s nephew, arrested in 2012 at the age of 17 for alleged participation in anti-government protests, had also been sentenced to death by crucifixion.

The inclusion of Nimr among the 47 executed Saturday came as a surprise to the administration. It was quickly followed by condemnation in Iran and the storming of the Saudi Embassy there. On Sunday, Saudi Arabia severed relations with Iran. A number of Sunni governments followed suit.

“This domestic balancing game is really where we should focus in the sense that the royal family is under pressure for siding with the United States against the Islamic State and the need to show they’re tough on Iran as well,” Wehrey said. “Nimr has been the object of so much vitriol and hate from the Sunni establishment, he was an easy target, someone they could use to temper some of the pressure from the clerics.”

With no chance to undo the execution, Kerry and other U.S. officials who have communicated with the Saudis have focused on trying to walk back the breach in diplomatic relations. So far, the Saudis have not agreed, officials said, but they have not said no. The administration also believes that it has received some assurance that Nimr’s execution will not be followed by a similar fate for his nephew.