BARACK OBAMA already faced a long and tricky agenda for his visit to Saudi Arabia scheduled for later this month. Sixty-nine years after Franklin Roosevelt and King Abdul Aziz bin Saud, the country’s founder, forged an alliance aboard an American cruiser in the Suez canal, the two nations find themselves at odds not only over such perennial irritants as Israel and human rights, but increasingly over newer issues, from Gulf security to the Syrian civil war and to post-revolutionary troubles in another prickly ally of America, Egypt.

Saudi Arabia has now added yet another complication. Along with its close allies Bahrain and the United Arab Emirates (UAE), the kingdom on March 5th abruptly recalled its ambassador to Qatar. That small emirate, which juts out of Saudi Arabia like a tiny thumb from a big fist, is not only a fellow member of the Gulf Co-operation Council (GCC), a six-country club of oil-rich Arab monarchies. Qatar also happens to host the Combined Air and Space Operations Centre, the most critical of the constellation of American military bases around the Gulf, together serving some 35,000 American troops, that have long shielded the GCC and acted as a prod to their mutual foe, Iran.

This diplomatic tiff between Arabs may well be contained. After all, Saudi Arabia suspended ties with Qatar for several years in the 1990s in anger at the overthrow of a friendly emir by his son, Sheikh Hamad al-Thani, father of the current ruler, Sheikh Tamim. Qatar responded to the latest rebuke with mild “regret and surprise”, saying its own envoys would stay put in “brotherly” GCC capitals.

Cut them off?

But the row has been brewing for some time, and could get worse. Rumours suggest the Saudis have quietly threatened to seal their border with Qatar, the emirate’s sole land link to the outside world, as well as to close Saudi airspace to Qatar-bound flights. This would bother the Americans, who co-ordinate all their military activity in the air space between Syria and Afghanistan from their base in Qatar.

The reasons for Saudi fury are plain. Starting with the launch of Qatar’s noisy Al Jazeera satellite channel in 1996, the emirate’s openness to Arab political dissenters (except from within the emirate itself) has rubbed up against its autocratic neighbour. Anger grew with the outbreak of the Arab spring in 2011, not only because the Saudis (and most other Arab monarchies) saw the uprisings as a threat, but because Qatar has doggedly and generously backed the re-emergent Muslim Brotherhood in every ensuing contest, from Libya and Tunisia to Egypt and Syria. The Saudis, and perhaps even more so the UAE, have long viewed the Brotherhood as a subversive cult whose pan-Islamic ideology and secretive, cell-like structure pose a singular danger.

When the Brothers won elections in Egypt in 2012, Qatar poured in money to prop up their man, President Muhammad Morsi. Since Egypt’s generals overthrew him last year, the Saudis, Kuwaitis and other allies have sloshed in far more cash. Qatar, meanwhile, has served as a haven for fugitives from Egypt, including hardened jihadist extremists as well as besuited Brotherhood politicians. Al Jazeera’s Arabic channels, demonised in Egypt to the point that staff in its independently run English-language division are being tried as terrorists, have become lonely pulpits for the Brotherhood. Al Jazeera’s star preacher, Yousef al-Qaradawi, rails against Arab regimes that he says were complicit in the “crimes” of Egypt’s coup leaders. Mr Qaradawi lives happily in Qatar.

An explanatory joint statement from Saudi Arabia, Bahrain and the UAE accused Qatar of breaching a pledge, made by Sheikh Tamim in November, to tone down such invective and “abide by the principle of non-interference in other countries’ internal affairs”. Less officially they are said to be demanding the expulsion or extradition of Islamist exiles. On March 3rd a court in the UAE sentenced a Qatari doctor to seven years in prison for alleged conspiracy, in the latest of several trials targeting suspected Brotherhood cells. Saudi Arabia for its part recently banned Brotherhood works from the Riyadh Book Fair and blocked suspected members from preaching in mosques.

Mr Obama will have to tread carefully. He must convince Iran that America’s Gulf alliance remains strong, while persuading fissiparous Arab doubters that America, hoping for a nuclear deal with Iran and simultaneously reducing its armed forces and seeking to “pivot” towards Asia, has not gone soft on what the Arabs see as a Persian threat. Mr Obama must also explain his reticence to help either Syrian rebels or Egypt’s generals, even as his Gulf allies press for a bigger commitment. Mr Roosevelt, by comparison, had it easy.