“Whether we can get Mr. Obama to change his mind, I don’t know,” Prince Turki said.

Syria is not the only Saudi grievance against the Obama administration. With Egypt, the Saudis were angry that Washington turned on its longtime ally, President Hosni Mubarak, and accepted the election of an Islamist, Mohamed Morsi of the Muslim Brotherhood. The Saudis were again upset that the United States suspended some aid after the military overthrew Mr. Morsi in July.

While Washington may have felt it had no choice but to support the millions who poured into the street calling for Mr. Mubarak’s ouster and to show some displeasure with a military takeover, the Saudis saw the United States as having let down an ally in support of the Islamists, twice.

The Saudis also feel slighted by Washington’s seeming eagerness to reach a nuclear deal with Iran — negotiations they feel they should be a part of. Iran is Saudi Arabia’s nemesis in the region, and the Saudis are worried that Washington is again being naïve in trusting that Iran will offer a sincere and verifiable compromise with its nuclear program.

But Syria has been a special concern for Saudi Arabia’s monarch, King Abdullah, Saudi officials say, for two reasons. He feels responsible for halting the wide-scale killing of his fellow Sunni Muslims. And Syria has become the most important battleground, in Saudi eyes, for the perennial conflict with Iran, which is seen here as almost an existential threat to the kingdom because of its goal of exporting its own brand of revolutionary Shiite Islam across the Muslim world.

“Saudi Arabia cannot afford to be encircled by Iran, from Iraq and Syria. That is out of the question,” said Khalid al-Dakhil, a political sociology professor at King Saud University who has called for Saudi Arabia to become less dependent on the United States.

The Saudis were initially reluctant to provide military support to the rebels in Syria after the uprising turned into an armed opposition movement in 2011. The interior minister, Muhammad bin Nayef, was against it, and cited the concern that money and arms could flow to jihadists, according to a Western diplomat who spoke with him at the time.

The Saudis began funneling arms to the rebels in 2012, but provided light weapons only, largely out of concern that heavier weapons could get into the hands of jihadists. They mostly worked through middlemen, including Lebanese political figures who had long been part of their patronage network. But that approach hampered their effectiveness, with much of the money landing in foreign bank accounts instead of buying weapons for the rebels.