Last week’s eruption of palace intrigue in Jordan, in which King Abdullah placed Prince Hamzah, his restless half-brother, under house arrest, is ominous. So are signs of meddling by Saudi Arabia.

What Amman says was a plot threatening the “security and stability” of the country, and the king calls sedition, has been contained, for now. If the Saudis were indeed involved in this affair — and the Jordanian government is convinced they were — both sides seem resolved to paper it over. But the future of Jordan, the west’s oldest and most steadfast Arab ally, is under a cloud.

Often described as a haven of stability in a region of endemic turmoil, Jordan is sandwiched between the Levant and the Gulf, with Syria to its north, Saudi Arabia to its south, and flanked by the cauldrons of Israel/Palestine and Iraq. As the late King Hussein showed, its rulers need not just good luck and shrewd judgment, but to tack with regional winds that episodically howl through Jordan.

King Abdullah was a surprise choice to succeed Hussein in 1999, selected mainly because he was the blooded commander of the elite special forces, the intersection of the army and intelligence services that underpin the Hashemite monarchy. The young Prince Hamzah, eldest son of King Hussein and his fourth wife Queen Noor, was named crown prince, but displaced as heir apparent in 2004 by Prince Hussein, first son of Abdullah. Thus began a saga of thwarted ambition and sibling rivalry.

Prince Hamzah, who looks, speaks and dresses like his father, is popular. Although powerless, he has cultivated the native Jordanian tribes. These East Bank tribes, rather than the Palestinian majority of West Bank origin, are the bedrock of the regime. But they regularly stage uprisings; and the financially squeezed army is really tribesmen in uniform.

King Abdullah lacks his father’s regal populism or paternalist charm. More importantly, Jordan, a proud country often reliant on handouts, can no longer afford the social contract whereby East Bankers are guaranteed state jobs in the military and civil service while Palestinians run a weak private sector. Prince Hamzah last week railed on video about “the corruption and . . . incompetence” of “the last 15 to 20 years”. These charges resonate, particularly in the loyalist south.

King Abdullah and Jordan’s pivotal role in regional diplomacy were, furthermore, undermined by ex-president Donald Trump and his close allies in Israel, Prime Minister Benjamin Netanyahu, and Saudi Arabia’s Crown Prince Mohammed bin Salman.

Trump’s promotion of the Israeli right’s wish list, including recognising Jerusalem as the capital and assent to Israel annexing Jewish settlements in the occupied West Bank, destabilised Jordan by raising the spectre of a new wave of Palestinian refugees. As Israeli ties with the Gulf strengthen, Jordanians sense the House of Saud wants to take oversight of Jerusalem’s Islamic sites from the Hashemites — from whom Crown Prince Mohammed’s grandfather took the holy cities of Mecca and Medina in 1925 — as the price of detente with Israel.

King Abdullah was the first Arab leader called by then president-elect Joe Biden, who put off talking to Netanyahu for months and refuses to deal with Crown Prince Mohammed. Biden and US allies should make clear that dabbling with Jordan’s stability is a red line. But the king now has a platform of grievances laid out by Prince Hamzah, echoing the complaints of the East Bank tribes but which reflect the malaise of Jordan. He would be wise to address them.