RIYADH, Saudi Arabia >> The images of the past year have been deeply unsettling for the people of Saudi Arabia, long accustomed to oil-fueled prosperity and regional clout: militants firing at communities along the country’s southern border; protesters storming the Saudi Embassy in Tehran; civil wars raging in three nearby states.

The view from Riyadh has become increasingly bleak as stubbornly low oil prices constrain the government’s ability to respond to crises and as the kingdom’s regional rival, Iran, moves aggressively to expand its influence at Saudi Arabia’s expense.

Under huge stress, the Saudis have responded in unpredictable ways, often at odds with Washington’s interests. They have launched a costly military offensive in neighboring Yemen that has failed to defeat the Houthi rebels and has empowered the al-Qaida affiliate there. They have executed dozens of men on terrorism charges, including a prominent dissident Shiite cleric. And they have largely walked away from Lebanon, suspending billions of dollars in promised aid as Iranian influence there grows.

This is the Saudi Arabia that will greet President Barack Obama, who is scheduled to arrive in Riyadh on Wednesday and who is the source of no small share of this nation’s anxiety. Policymakers across the kingdom have long said that they feel Obama does not share the country’s regional interests. And after he criticized the Saudis as “free riders” last month, those suspicions have hardened into fears that he may be actively undermining them.

Obama may try to use his visit to mend relations, but it remains unclear how badly the ties that have long bound the United States and the Saudi monarchy have weakened, and whether the damage can be repaired.

“It is a concerning factor for us if America pulls back,” said Prince Turki al-Faisal, an outspoken member of the Saudi royal family, a former head of intelligence and a former ambassador to the United States. “America has changed, we have changed and definitely we need to realign and readjust our understandings of each other.”

The moment is a perilous one for the Saudis as they face economic and demographic challenges as well as strategic and security concerns.

Domestically, a growing cohort of young Saudis is entering the job market as low oil prices constrain economic opportunities and undermine the welfare system. Regionally, Iran has outflanked and outmaneuvered Saudi Arabia in crucial countries as the Arab Spring and the war in Syria have upset the local order. Globally, the drift of the United States away from the monarchy’s side has made the Saudis realize how much they have relied on the world’s most powerful nation.

“A large number of factors have come together, both in the region and at home, to create a very challenging threat environment for the Saudis,” said Lori Plotkin Boghardt, a fellow at the Washington Institute for Near East Policy. “The Saudis feel under siege.”

For decades, the kings and princes who rule Saudi Arabia wielded their oil wealth and religious clout as the controllers of Islam’s holiest sites to pull strings and fund proxies across the Arab world and beyond.

Since the kingdom has never had the military might to protect itself, its alliance with the United States has been essential, and hugely beneficial to both sides. Saudi Arabia knew that in exchange for a steady flow of oil and billions of dollars for the American arms industry, the U.S. would come to the rescue if its ally faced an external threat — and that it would never speak out too loudly about the kingdom’s closed political system or its poor human rights record.

That relationship was unsettled by the Arab uprisings of 2011, when Saudi officials saw the U.S. cut loose another Arab ally, President Hosni Mubarak of Egypt, amid popular protests. Since then, frustration among Saudi officials has grown as Obama limited American engagement in later crises, in Libya, Syria and elsewhere, and as he made a deal with Iran to lift sanctions in exchange for the reining-in of its nuclear program.

In Syria, the Saudis saw the uprising against President Bashar Assad as an opportunity to replace an Iranian ally who was killing his own people. The hope was that a government more amenable to Riyadh’s influence, and less to Iran’s, would come to power. But that hope dwindled when the U.S. backed away from military action after Assad crossed Obama’s “red line” against the use of chemical weapons.

Over time, it became clear that Obama had prioritized combating the Islamic State over ousting Assad. This infuriated Riyadh, which wanted to marry the two causes. Privately, Saudi officials blame Obama for prolonging the war by barring Saudi Arabia and other countries from giving Syrian rebels more powerful arms, like anti-aircraft missiles, which Obama feared could be used outside Syria by terrorists.

The mounting frustration has led Saudi Arabia, under a new monarch, King Salman, to abandon its quiet checkbook diplomacy and lash out. In January, it executed 47 men on terrorism charges, including al-Qaida militants and the Shiite cleric — sending what it thought was a message to deter jihadis and Iran from trying to destabilize the kingdom.

Analysts have begun speaking of a “Salman Doctrine,” although it is mostly associated with the king’s son Mohammed bin Salman, 30, who is the defense minister and is second in line to the throne. The doctrine calls for increased self-reliance and more assertiveness in regional affairs.

Last month, Saudi Arabia suspended $4 billion in aid promised to the Lebanese army and security forces, saying that Hezbollah, the Iranian-backed Shiite militant organization in Lebanon, had become too powerful. The Saudis and their Persian Gulf allies also issued travel warnings, depriving Lebanon of Gulf tourism dollars.

Those moves surprised U.S. officials, who have reported no change in the security situation in Lebanon and who continue to support the Lebanese army as a counterbalance to Hezbollah.

Saudi Arabia has also shown a growing willingness to use direct force. Last year, its military spending grew to $87.2 billion, as the country passed Russia to become the world’s third-highest military spender. Last month, it opened a new arms factory, and it has proposed building a military base in Djibouti, on the Horn of Africa, to project power abroad. Mohammed has also spearheaded the creation of an international alliance of Muslim countries to combat terrorism, although it is unclear when — if ever — it will begin operations.

Diplomats who track the kingdom question whether Saudi Arabia has the strategic capabilities to match its new ambitions.

One test case is Yemen, where the kingdom and its allies have carried out a bombing campaign for more than a year, trying to oust the Houthi Shiite militant group from the capital and restore the government — at tremendous cost to the people of Yemen. An estimated 6,400 people have been killed, more than half of them civilians; nearly half the country’s provinces are on the verge of famine; and al-Qaida has expanded its control in the south.

The Saudis defend the war as essential to their national security. “It is a war of necessity,” said Abdulaziz Sager, a Saudi political scientist and the chairman of the Gulf Research Center. “You can’t let a failing state with a violent nonstate actor be your neighbor.”

Domestically, the fall in oil prices has echoed through the Saudi economy, forcing the government to run a large deficit, impose spending limits and ponder steps that were once unthinkable, like imposing taxes on citizens and privatizing parts of Saudi Aramco, the state oil giant.

Fitch Ratings and Standard & Poor’s have downgraded the country’s credit rating this year, and companies that depend on government contracts have struggled to pay workers, creating problems for citizens and for the kingdom’s many foreign workers.

“These are really uncharted waters,” said Plotkin Boghardt, the Washington Institute fellow. “The oil income has been like the superglue between the Saudi government and the Saudi citizens. With this glue beginning to melt away, it opens up a whole situation that we’ve never seen before and they’ve never been in before.”

It is not all dire news for the kingdom. Saudi Arabia still has the world’s largest reported reserves of oil, which remains essential to the global economy. The country also has low debt and large cash reserves.

And although Iran has increased its influence in Lebanon, Syria and Iraq, it has done so at great cost, financially and militarily. “The Saudis took the region for granted while Iran put a strategy in place back in the ’80s, and has been implementing it year by year and dollar by dollar,” said Randa Slim, an analyst at the Middle East Institute.

But the kingdom maintains strong ties with many other countries — including Egypt, Britain and Pakistan — and as a leading Sunni nation, it has the demographic upper hand against Shiite Iran. “The score is still in their favor because it is a majority Sunni Arab region,” Slim said.

Officials involved in the Saudi-U.S. relationship acknowledge the chill, but say that it has not filtered down to the operational level, and that cooperation remains robust on issues like security, counterterrorism and business. And many Saudis realize that Obama’s days in the White House are almost over and that his successor may engage differently with the kingdom.

“I’ve read so many accounts over the years predicting the demise of the House of Saud, and each time they’ve managed to survive,” said Robert W. Jordan, a former U.S. ambassador to Saudi Arabia. “They have an enormous survival instinct.”

© 2016 The New York Times Company