Jacquelyn Martin, Pool, Associated Press
U.S. Secretary of State John Kerry, left, walks with Saudi Foreign Minister Prince Saud al-Faisal, on arrival in Riyadh, Saudi Arabia on Sunday, March 3, 2013.

RIYADH, Saudi Arabia — Saudi Arabia, one of the oldest U.S. allies in the Middle East, is increasingly uncomfortable with the policies President Barack Obama is pursuing there.

At functions in Riyadh and on the local editorial pages, it's becoming common to hear criticism of the United States. The decision to back away from strikes against Syria was widely condemned by Saudis, who have backed the rebels fighting to oust Bashar Assad's government and pushed for military action in their support.

Signs of a U.S. thaw with Iran, Saudi Arabia's main regional rival, have heightened the concern in the world's biggest oil exporter. One result may be that the Saudis, who have worked with the U.S. to build up the Syrian political opposition, may start acting independently of their ally, said Mustafa Alani, an analyst at the Gulf Research Center in Geneva.

Saudi leaders from now on will "look at their own interests and act accordingly, whether the U.S. likes it or not," Alani said. "The Saudis have more or less respected the U.S. veto for the past two years for supplying arms to the Syrian rebels. I don't think this will happen any more."

The differences over Middle East policies may not shift the bedrock of business ties on which the Saudi royals built a U.S. alliance with roots in World War II, when King Abdul-Aziz Al Saud and President Franklin D. Roosevelt met aboard the USS Quincy.

Since the oil embargo of the mid-1970s, most disagreements between the countries haven't disrupted trade. Saudi Arabia has opposed U.S. support for Israel, and backed rulers seeking to repress protests in Egypt and Bahrain where the U.S. called for dialogue. The relationship also faltered after the Sept. 11 attacks, in which Saudi citizens were involved.

Through all those crises, the relationship based on oil and security has largely endured. Trade jumped 21 percent to a record $77.3 billion last year, making the desert kingdom the U.S.'s eighth-biggest partner, ahead of Brazil and France. San Francisco-based Bechtel Group Inc. got a $9.4 billion contract to build a new metro in Riyadh, and Lockheed Martin signed an accord last year to develop Saudi Arabia's national science agency.

Last month 1,100 businessmen and officials from both countries met in Los Angeles to expand commercial ties. "The main takeaway was that the U.S.-Saudi relationship is on a solid footing," said John Sfakianakis, chief investment strategist at Riyadh-based investment company MASIC, who was at that forum. "The U.S. brought their expected big guns, and the Saudis brought their fair share."

There's less harmony when it comes to regional diplomacy, though. Warning against the chemical weapons accord backed by the U.S. and Russia, Saudi Foreign Minister Prince Saud al- Faisal said Assad's government may use it as an opportunity "to impose more killing and to torture its people."

The Saudi minister pressed for a United Nations Security Council resolution that would include a mechanism for enforcement if Syria failed to disarm. He didn't get it. The resolution approved on Sept. 28 didn't spell out immediate consequences for non-compliance, nor did it assign blame for the Aug. 21 chemical attack near Damascus that killed hundreds.

As a result of such decisions, "Saudis think that the Americans don't care about what is happening" in Syria, Khalid al-Dakhil, a political science professor at King Saud University in Riyadh, said in a phone interview on Sept. 25. "The perceptions in Saudi Arabia are very negative about America's Syrian policy."

A cartoon in Saudi-owned Asharq Al-Awsat newspaper on Sept. 26 showed U.S., French and Iranian figures dipping into a blood- soaked flag of the Syrian Free Army, the main rebel military unit, and using it to color in their own flags.

More than 100,000 people have been killed in the conflict in Syria, and about 2 million Syrians have registered as refugees or are pending registration, the U.N. estimated in July.

For Saudi Arabia, the conflict has developed into a proxy war with Shiite-majority Iran, Assad's ally, part of a broader sectarian conflict between the Persian Gulf's main powers for sway over a region that produces a third of the world's oil.

Saudi King Abdullah urged the U.S. to attack Iran, "cut off the head of the snake" and halt its nuclear program, U.S. diplomats reported in cables released by Wikileaks.

Obama has favored sanctions and diplomacy with Iran, as with Syria, squeezing the country's oil output and pushing for curbs on its nuclear program. Last week he spoke by phone to his Iranian counterpart Hassan Rouhani, the first such conversation since the Islamic republic's creation in 1979.

"Saudi foreign policy is becoming more bellicose and more extroverted," while the opposite is happening in the U.S., Paul Sullivan, a Middle East specialist at Georgetown University in Washington, said in response to emailed questions. "U.S.-Saudi relations remain strong, but the Saudis seem increasingly wary by how much sway domestic politics has on U.S. policies on Iran and Syria."