RIYADH, Saudi Arabia — Persian Gulf leaders, led by King Salman of Saudi Arabia, are sending increasingly public messages of displeasure with the Obama administration over its policies in the Middle East, even as the president seeks to reassure them this week in meetings at Camp David.

Yet, while they are upset with the White House, particularly over the impending nuclear deal with Iran, the Saudis and their gulf allies face a dilemma: Even as they are taking a more active role in their own defense, they remain almost entirely reliant on Washington for their security.

This dependency “has to change, and they know this has to change,” said Jean-Francois Seznec, a professor of Persian Gulf political economy at the School of Advanced International Studies at Johns Hopkins University.

Decades of cooperation and billions of dollars in weapons contracts have left the gulf nations deeply entwined with the United States and Britain in ways that cannot be quickly undone, analysts say. Qatar hosts the largest United States air base in the region, and Bahrain is the home port of the Navy’s Fifth Fleet. And their efforts to make reliable military partners of fellow Muslim nations like Pakistan and Egypt have met little success, despite tens of billions of dollars in aid.

American-made fighter jets are being used in the Saudi-led bombing campaign in Yemen, but “none of these airplanes would fly if the United States refused to send parts,” Dr. Seznec said.

Many of the same fears driving the Saudi policy shifts have been expressed forcefully by Prime Minister Benjamin Netanyahu of Israel. Both capitals are worried that President Obama’s focus on achieving an agreement with Iran, a country they see as an implacable aggressor, has shaken bedrock commitments by Washington that have long underpinned the regional order.

The sense of neglect by Washington has caused a crisis of confidence among the gulf nations, capped by the announcement Sunday that King Salman of Saudi Arabia would not attend this week’s meeting — after the White House said that he would. The Saudi foreign minister, speaking Monday in Washington, said the decision was not related to any disagreement between the countries.

The king of Bahrain will also stay away, sending his crown prince instead. Of the six members of the Gulf Cooperation Council, only the monarchs of Kuwait and Qatar will attend.

American officials, trying their best to play down the incident, said Mr. Obama spoke with the king by phone on Monday in preparation for the meeting. But the Saudi king’s displeasure was clear.

“It is a diplomatic message that Saudi Arabia is not expecting anything new from Camp David,” said Abdullah al-Shammari, a Saudi political analyst and former diplomat. “Everyone knows that Saudi Arabia is not pleased with the administration of President Obama, especially when it comes to the deal with Iran and the nuclear program.”

Expressing an increasingly common view, he said the solution for Saudi Arabia was to depend less on the United States and to increase cooperation with other powers.

 

But the Saudis remain heavily reliant on the United States, and to a lesser extent on Britain, in nearly every branch of their security apparatus.

“The Saudi air force could not carry out day-in, day-out bombing missions without help from U.S. trainers and maintenance experts and the flow of spare parts and ammunition,” said Bruce Riedel, senior fellow at the Brookings Institution, speaking about the Saudi-led bombing campaign against Shiite rebels in Yemen.

A recent report by the Congressional Research Service said Saudi Arabia’s decision to update and expand its air force with American F-15 fighter jets would perpetuate Saudi reliance on parts and training provided by the United States military and defense contractors.

The United States is also involved in training the army and modernizing the Saudis’ national guard, and American advisers paid for by the Saudi government are “embedded in industrial, energy, maritime and cybersecurity offices within the Saudi government,” the report said.

Saudi Arabia, the United States and Britain also have close intelligence ties, with top officials from the three countries meeting frequently and sharing information.

In addition, contracts for fighter jets include agreements on maintenance, spare parts and software upgrades that can go on for years, Mr. Riedel said, keeping the countries’ security operations bound tightly together far into the future.

Dr. Seznec, of the School of Advanced International Studies, estimates that Saudi Arabia has spent about $500 billion to build its military in the last 20 years. About three-quarters of that money has gone to the United States.

“Those are huge amounts of money,” he said.

Gulf nations are concerned that President Obama is so fixed on securing a nuclear deal with Iran that he has overlooked Tehran’s misbehavior in the region, particularly its empowerment of its allies and proxies in Iraq, Syria, Lebanon and Yemen.

Gulf nations worry further that any sanctions relief that results from an agreement will give Iran even more money to fund its proxies.

“We assume the worst-case scenario, which is that Iran will continue to run its foreign policy in terms of more intervention and with the clout that Iran will feel as a result of having this agreement,” said Sami al-Faraj, head of the Kuwait Center for Strategic Studies. “The United States today has left us in a sense alone.”

Some gulf nations have made efforts to diversify their alliances.

Qatar recently signed a multibillion dollar weapons deal with France, and similar deals with other nations are reportedly on the way. Persian Gulf leaders have so appreciated France’s hard line in the Iranian nuclear talks that they invited President François Hollande to attend a meeting last week of the Gulf Cooperation Council, making him the first head of state from outside the alliance to do so.

While Qatar, with its relatively small military, can shift quickly with new arms deals, it would take Saudi Arabia much longer to integrate military hardware from another supplier, Mr. Riedel said.

Saudi Arabia has, however, asked for help from fellow Muslim countries like Pakistan in its Yemen campaign. But despite bankrolling the Pakistani nuclear program and offering other aid over the years, the Saudis were shocked when the Pakistani parliament unanimously voted not to send troops.

Egypt, whose government has been kept afloat by billions of dollars in Persian Gulf aid in recent years, has also declined to send ground troops.

Despite the reluctance of would-be allies to step up, the gulf nations appear to be at the beginning of what could be a long process of learning to rely more on themselves and other allies.

“They would prefer for the U.S. to be the godfather and protector, but they also realize that they have to stand on their own feet,” Dr. Seznec said.