RIYADH, Saudi Arabia -- The historic 15-minute phone call between President Barack Obama and Iranian counterpart Hassan Rouhani may have cost the U.S. one of its key friends in the Middle East.
The U.S. and Saudi Arabia have been allies for some 80 years, with the U.S. offering military protection to the world’s second-biggest oil producer.
But as relations warm between Tehran and Washington, Saudi Arabia last month signaled that it will "shift away from the U.S.," giving Secretary of State John Kerry plenty to discuss with King Abdullah when they meet on Monday.
Riyadh is deeply skeptical of Iran's charm offensive and frustrated by an alleged lack of consultation over Washington's changing stance toward a country once branded as a member of the so-called "axis of evil."
Only five years ago, the Saudis urged the U.S. to strike Iran -- which is situated just across the Persian Gulf from the kingdom. The Saudi government fears that the development of an Iranian nuclear weapon would seriously threaten its national security.
The extent of Saudi frustration at being left out in the cold by the U.S. became apparent last month when it rejected a seat on the United Nations Security Council. It was the first country to do so, and the move surprised even its own diplomats who had been preparing for the role for years.
Outwardly, Saudi Arabia directed its anger at the U.N., criticizing its "double standards" in failing to resolve the crisis in Syria and long-running tensions between Israel and Palestine.
But the autocratic monarchy’s frustration is primarily with the U.S. after what it sees as a series of snubs, a source with knowledge of Saudi foreign policy told NBC News.
"At the end of the day we know what friendship is all about," the source said, speaking on the condition of anonymity. "But if diplomacy starts with your friends and you don’t consult them then that is obviously going to give rise to suspicion."
Though the two countries have been allies since the 1930s, the threatened "shift" in relations with the U.S. follows decades of pressure from the Saudi public to distance their country from the superpower.
Many citizens feel aggrieved by perceived White House failures to solve the Palestinian-Israeli conflict. And American foreign policy in the region, particularly when it comes to the interventions in Iraq in 1990 and 2003, is seen by many as disastrous.
But those sticking points were previously not enough for the Saudi government to act against its ally.
The U.S. agreement with Russia not to strike Syrian President Bashar Assad in response to August's alleged chemical weapons attack, but instead to remove his chemical weapons arsenal, also angered Riyadh.
Iran has traditionally backed Assad's regime, while Saudi Arabia has funded Syria's predominantly Sunni opposition.
“The most important thing between allies is that they strategize together before declaring any decisions,” the source told NBC News. “The Kerry-Lavrov agreement has clearly shown that the Americans want to reshape the Middle East without consulting us. You can’t just forego strategic alliances like that and claim to be allies without any form of consultation.”
The Saudi administration felt further shunned when the U.S. decided to reach out to Iran following the election of Rouhani, who has seemingly adopted a more moderate agenda than his predecessor Mahmoud Ahmadinejad. In a September interview with NBC News' Ann Curry, Rouhani said Iran would never develop nuclear weapons and insisted that his country was not "looking for war."
Despite Tehran's insistence that its nuclear program is for peaceful purposes, Saudi Arabia has long harbored concerns. According to a diplomatic cable published by Wikileaks, King Abdullah urged the U.S. to “cut off the head of the snake” and strike Tehran in 2008.
Like Israeli President Benjamin Netanyahu, who has described Rouhani a "wolf in sheep’s clothing," Saudi Arabia isn't convinced by Tehran's overtures.
Saudi Arabia is trying to express their disappointment by flying solo -- expressed in the historic rebuttal of the U.N. seat.
Some Saudi citizens feel the change in tone is overdue.
“Well it’s about time that we distanced ourselves from the U.S.,” a Saudi businesswoman told NBC News, speaking on condition of anonymity. “When you rear a pet snake, the least that you can expect is that you will eventually be bitten. I just don’t understand why we had allowed ourselves to become so dependent."
The U.S. has been quick to try to tackle the sudden deterioration of relations.
Speaking at the U.S. Embassy in Riyadh before meeting with King Abdullah on Monday, Kerry described the Saudis as "the senior players in the Arab world."
He added: "Egypt is in transition, so the Saudi role is more important. They can influence a lot of things we care about.... we are working together on Middle East peace, on Syria, on Iran."
Kerry is visiting Riyadh as part of a nine-day tour of the Middle East.
Saudi Foreign Minister Prince Saud al-Faisal also hosted Kerry at his private residence in Paris on Oct. 21.
A senior State Department official told Reuters that Kerry had discussed with al-Faisal the advantages of being on the U.N. Security Council, while making it clear that "it is Saudi Arabia's decision to make."
Speaking in London on Oct. 22, Kerry said the U.S. and Saudi Arabia "agree on a great deal."
A day later, White House spokesman Jay Carney also acknowledged "disagreements on some issues" with Saudi Arabia but said the "relationship is very important economically and in national security ways."
And on Oct. 24, State Department spokeswoman Marie Harf told a press briefing that the U.S. has "a very strong relationship with the Saudis and will continue to."
She added: "Sometimes we have disagreements, we do with everyone. That’s why we talk through them, and that’s why we’re trying to get to a place where we can work together on these issues."
Washington's next move is crucial, according to Sir Tom Phillips, associate fellow at think tank Chatham House’s Middle East and North Africa program.
"[Saudi Arabia] will be looking to see if the West is dealing with the [Syrian] chemical weapons for its own benefit, or for the benefit of regional stability," he said. "And then of course they will be watching the Iran agenda very closely to see if there is going to be a deal with Iran and whether anything will be given away."
But asked if the rift could have serious long-term implications, Sir Tom said: "I don’t think so. Who is Saudi Arabia going to turn to? China and Asia are a major market for them, but you would have to ask what would be the American response? It probably wouldn't get to that."
Shashank Joshi, a research fellow at the London-based Royal United Services Institute, added: "The Saudi Arabians do not have enough leverage to prevent all these things they fear, so they have to swallow what the Americans give them."
He said that the mutually beneficial relationship of U.S. military protection and Saudi oil production is too valuable to be threatened by diplomatic differences.
"It is much less serious than Saudi Arabia would like us to believe."
NBC News' Alexander Smith reported from London. Reuters contributed to this report.