Yemeni protesters shout slogans during a demonstration in the strategic city of Taez on March 28, 2015, in support of the Saudi-led 'Firmness Storm' operations against Shiite rebels. (-/AFP/Getty Images)

President Obama has for years stuck to a strategy aimed at keeping the United States from getting pulled into a big regional war between Iran and America’s traditional Arab allies.

The net result was a tailored, country-by-country approach to the region’s turmoil that put a priority on nuclear negotiations with Iran and the fight against terrorism. Containing Iranian proxies took a back seat.

As chaos and sectarian bloodshed have spread, the White House is facing heavy pressure from its traditional Sunni Arab allies, Congress and some in the U.S. military to confront Iran more forcefully over its support for militant groups.

Such a pivot carries big risks for the White House, which doesn’t want to be drawn into a worsening conflict between Sunnis and Shiites that its policies didn’t start and that it cannot stop. “We’ve always had concerns about Iran’s destabilizing behavior and abetting some of the worst actors in the region,” said a senior administration official who was authorized to speak on the issue, but not be quoted by name. “We also have a realization of the precise limitations of how much we can impact that behavior.”

In recent days Saudi planes and Egyptian warships have launched attacks against Iranian-backed Shiite rebels in Yemen. The United States has supported the Saudi attacks with intelligence and logistical help.

Saudi Arabia enters Yemen conflict
Saudi Arabia launched airstrikes Thursday in Yemen to repel Shiite Houthi rebels threatening the southern city of Aden.

(Gene Thorp/The Washington Post/Source: American Enterprise Institute, news reports)

In Iraq, the United States has pressured Prime Minister Haider al-Abadi to disentangle Iranian-supported militias from government forces in exchange for the firepower of U.S. warplanes over the city of Tikrit. The Iraqi army, along with militias and Shiite volunteers, has been locked in a bloody, month-long stalemate there with Islamic State insurgents.

“Our actions have sought to marginalize the worst of the Shiite militias,” the administration official said of the Iranian-backed fighters. “They are standing on the sidelines and not invested in the Iraqi project.”

To critics, though, the push to confront Iran has come too late and at far too high a cost to regional stability. The administration has “finally and belatedly” started to talk about the threat that Iran poses to the region, said Tamara Wittes, a former top Obama administration State Department official and director of the Center for Middle East Policy at the Brookings Institution.

Saudi Arabia and other Gulf countries say the Obama administration’s tepid response to the conflict in Syria, for example, enabled the unchecked rise there of fighters sponsored by Iran, as well as Islamist militants.

“We see Iran involved in Syria and Lebanon and Yemen and Iraq and God knows where,” Saudi Foreign Minister Prince Saud al-Faisal said during talks earlier this month with Secretary of State John F. Kerry. “This . . . must stop if Iran is to be part of the solution of the region and not part of the problem.”

Some former senior U.S. military commanders, meanwhile, said they have been warning for years of the need to do more to deal with what they see as Iran’s efforts to sow chaos through its armed proxies. “The policy was benign neglect and turn the other cheek,” said retired Col. Derek Harvey, who served as a senior intelligence officer at U.S. Central Command. “We’ve consistently refused to do things to the worst of the worst guys over there.”

Ret. Marine Gen. James Mattis, who oversaw U.S. forces in the Middle East from 2010 to 2013, was among the most insistent voices inside the military pushing for a policy focused on punishing Iran and its proxies.

Mattis lobbied for more interdictions of ships and planes carrying Iranian arms to battlefields such as Yemen and Syria, said former defense officials, who spoke on the condition of anonymity to discuss policy deliberations. And Mattis pressed for more covert actions to capture or kill Iranian operatives, especially after the foiled 2011 plot by Iran to kill the Saudi ambassador at a Washington restaurant.

The former defense officials said plans to punish Tehran were often sidelined over concerns that they could disrupt negotiations to prevent Iran from developing a nuclear weapon.

“The Iranians showed that they could intervene everywhere even as they were negotiating on the nuclear issue,” said Ilan Goldenberg, who served as the Iran Team Chief in the Pentagon. Mattis’s pressing on the issue caused him to fall out of favor with the White House and ultimately led to his leaving command early, the former defense officials said.

“Some of Mattis’s ideas probably went too far,” Goldenberg said.

Mattis declined to comment for this story. In testimony before the Senate Armed Services Committee last month, he complained that the United States lacked a strategy for dealing with the Middle East and that its influence is at “its lowest point in four decades.”

Even if the United States had confronted Iran more, it is not clear it would have produced a more stable Middle East. The violent chaos upending the region is the culmination of decades of poor governance, economic deprivation and brutal crackdowns by dictators desperate to cling to power.

Following the Arab Spring, the White House set objectives on a country-by-country basis that reflected the complicated mix of forces driving the unrest in each country, and U.S. core interests. It backed swift military action against Libyan leader Moammar Gaddafi, but stopped short of doing the same with Syrian leader Bashar al-Assad.

In impoverished, heavily armed Yemen, American policy focused on destroying an al-Qaeda affiliate, which posed the gravest threat to the United States. Relatively little attention was paid to the rise of the Iranian-backed Houthis, who toppled the Yemeni government and forced the United States last week to pull out the last of its Special Operations troops and counterterrorism advisers.

Some praise the piecemeal approach as a modest, measured and pragmatic response to a crisis that will probably roil the region for decades to come. “The administration wants to be realistic about what the United States can actually achieve when the tectonic plates of the region are shifting so dramatically,” said Brian Katulis, a Middle East analyst with the left-leaning Center for American Progress.

He described the Obama approach as “ad hoc crisis management mode” at a time when no Middle Eastern nation “seems to have a realistic long-term vision and set of clear goals for what they want to see the region look like in five years.”

Other Middle East experts said the Obama administration’s efforts to avoid wading into sectarian civil war has unnerved the closest U.S. allies and emboldened Iran.

“A vacuum was created that Iran exploited,” Martin Indyk, executive vice president of the Brookings Institution and Obama’s former Middle East envoy, wrote in an e-mail. “Now we have to make a choice. Not taking a stand in Syria was the original mistake that helped to open the gates of hell.”

A U.S.-brokered agreement to prevent Iran from obtaining a nuclear weapon over the long term could help foster stability and calm the region, administration officials said.

In the near term, though, it seems likely to further roil relations with America’s Sunni Arab allies, some of whom worry that the deal is just the first step in a U.S. “Persian Pivot.”

The gradual lifting of economic sanctions would give Iran a cash windfall that it could use to foment further unrest through support for Syria’s Assad, Hezbollah and Palestinian militant groups, said Karim Sadjadpour, a senior associate at the Carnegie Endowment for International Peace.

Such a move by Iran could force the administration to take on a more aggressive role to reassure Sunni allies, such as Saudi Arabia, Egypt, Israel and Turkey, who feel “threatened by the chaos that surrounds them,” Indyk wrote. “The first priority is to reassure them that we are with them.”