SPEED is not generally associated with the hushed style of traditional Saudi diplomacy, yet the abruptness of the kingdom’s flip-flop on October 18th was stunning by any standard. In the morning, Saudi diplomats in New York were trumpeting their country’s election to a coveted two-year stint as a temporary member of the UN Security Council: a cause for rejoicing and a “defining moment” in the kingdom’s history, enthused the Saudi ambassador to the UN, Abdullah al-Mouallimi.

Yet within hours, word came from the Saudi capital, Riyadh, to cancel the celebration. In a step unprecedented since the UN’s creation, the kingdom declared that it would renounce the seat. The council had failed to bring peace to the Middle East, it said, noting in particular Palestine and the civil war in Syria. So membership would be refused until the council is reformed.

It is hard to understand how Saudi Arabia can advance a reformist agenda by shunning engagement with the very institution it says it wants to change. It is also hard to see how the decision squares with the months of lobbying and preparation the Saudis had put into their bid for the seat. At least a dozen Saudi diplomats had spent much of the past year training in New York for the expected wider duties of council membership.

So the reasons for the sudden Saudi move likely lie elsewhere, such as in Washington, DC. King Abdullah, now 89, is known for his occasional bursts of frank impatience with the kingdom’s oldest and strongest ally. Back in 2001 he penned a furious letter to America’s then-president, George Bush, over his perceived failure to tackle the Israel-Palestine issue, though this was swallowed in the turmoil following the 9/11 terrorist attacks. In recent months Saudi frustration with what it sees as a dithering, unreliable ally has swiftly mounted.

The kingdom strongly backed the military coup in Egypt in July that overthrew a Muslim Brother-led government. But rather than voicing the tacit support the Saudis expected, Barack Obama’s administration responded with wary prevarication and a reduction in aid. A second shock came with Mr Obama’s sudden moves towards rapprochement with Iran, a country the Saudis see as a hostile Shia power and a bitter regional rival. Years of patient effort to sustain and fortify an anti-Iranian front may now be wasted, the Saudis fear.

But the sharpest cause for kingly ire has been America’s failure to punish President Bashar Assad and his regime in Syria for breaching Mr Obama’s own much-touted “red line” against the use of chemical weapons. Not only did the pro-rebel allies lose a golden chance to trounce Mr Assad and roll back the influence of his main ally, Iran. The Americans’ perceived cowardice has also, in Saudi eyes, boosted the narrative of al-Qaeda-style radicals, who have said all along that the West was not to be trusted. Varied jihadists now threaten to take over the core of the armed opposition force, whose moderate wing the Saudis have assiduously cultivated, including by providing facilities on Saudi soil for American instructors to train Syrian fighters.

In Paris on October 21st and at a gathering the next day in London of the “Friends of Syria”, a group of 11 countries backing the opposition to Mr Assad, delicate meetings took place between Prince Saud, the Saudi foreign minister, and John Kerry, the American secretary of state, who sought to reassure each other that help from the West and from the Gulf goes to the less extreme of the Syrian rebel factions. Mr Kerry is said to have implored the Saudis to rethink their rebuff to the Security Council.

This will take more than sweet talk. Prince Turki al-Faisal, a long-time former head of Saudi intelligence, explained recently in Washington that the Saudis feel “a high level of disappointment in the US government’s dealings,” noting pointedly that “we never act impulsively.”

Some suspect that the Saudis, by rejecting the UN council seat, intend not to revert into shyness, but to adopt a more aggressive regional role. By this reasoning, they are not simply throwing up their hands in despair but are acting in the expectation of future clashes with the Security Council, perhaps over Iran and Syria. In recent months, commentators known to express publicly what princes say in private have hinted at a growing Saudi impatience for a bolder foreign policy. This could include a go-it-alone effort to topple Mr Assad.

Yet despite its immense wealth, the militarily feeble kingdom still needs friends, particularly in a world where oil prices may well decline. This could be another reason for its sudden reticence. Saudi Arabia has always preferred closed-doors diplomacy to open forums. A seat in the UN’s topmost council would have risked exposing, repeatedly and in full public view, a widening policy gap between the kingdom and its closest ally. This would not only represent a break with tradition, but could be seen in Riyadh as a strategic mistake that could be tricky to correct.

As if the secretive Saudis needed reminding of the perils of greater scrutiny, the UN’s Human Rights Council on October 21st castigated the kingdom for a slew of violations. Two leading watchdogs, Human Rights Watch and Amnesty International, submitted excoriating reports, noting the country’s failure to stop persecuting dissidents and to end discrimination against religious minorities and women (see our article above).