Washington: First the Saudis stocked up on weapons; now Qataris are stocking up on food. Welcome to the Middle East, where dictators and monarchs can be relied on to elevate regional rivalries over the bigger picture.

In quick succession on Monday, the Gulf states ganged up on fabulously wealthy but tiny Qatar, as Saudi Arabia, the United Arab Emirates and Bahrain, with Egypt and Yemen along for the ride, severed all ties with Qatar – in a second stab at their not-so-successful 2014 attempt to coerce Doha to embrace Riyadh's self-protective regional agenda.

In March of that year, the Saudis, the Bahrainis and the UAE accused Qatar of supporting the "terrorist" Muslim Brotherhood and interfering in the affairs of its neighbours, both in its policies and through its role as host to "hostile media" - in other words, the television network al-Jazeera.

This week they have again frozen diplomatic relations, ordering Qatari diplomats to quit their capitals within 48 hours. But this time, they upped the ante – cutting land, air and sea travel from Qatar; and ordering all their citizens to quit Qatar – save for Egypt, which depends on remittances from an estimated 350,000 Egyptian workers in the country.

Analysts attributed this display to a Saudi burst of self-confidence in the wake of US President Donald Trump's recent visit to the kingdom, during which Riyadh firmed orders for more than $US110 billion worth of US weapons.

But as news of the blockade spread in Qatar, there were reports of panic buying of essentials, driven by awareness that more than one-third of Qatar's food supplies are shipped from Saudi Arabia and the UAE.

With a sovereign wealth fund valued at as much as $US335 billion, Qatar can weather an economic crisis. But there were immediate warnings that Doha likely faces a steep hike in borrowing costs; will have to find complex trade and investment go-rounds; and as regional airlines abruptly halted flights to Doha, its own flagship Qatar Airways inevitably would become less attractive for travellers – because flight times would be longer as it sought routes outside what amounts to a Gulf exclusion zone, probably through Iranian and Turkish airspace.

But there's more. A call by Riyadh for global corporations to abandon Qatar was read as a bid to force executives to side with the regional heavyweight Saudi Arabia and its allies. Even as Australian producers put a dent in Qatar's claim to be the world's biggest exporter of liquefied natural gas, the likes of energy giant Shell and Exxon, which have invested billions in Qatar, could find themselves squeezed.

It's the gas revenue that funds much of the Qatari activity that unnerves the emirate's Arab neighbours, particularly its intervention in conflicts; it's funding of broadcaster al-Jazeera's provocative regional coverage; and its support for the Muslim Brotherhood and other Sunni Islamist movements that its equally undemocratic neighbours treat as an existential threat.

But it's complicated – especially for Washington as it tries to hold a regional coalition together in the war on Islamic State at the same time as it champions a regional, Saudi-led effort to contain Iran.

The US runs much of its air operations against IS in Syria and Iraq from the huge al-Udeid Air Base in Qatar, the biggest military facility in the region, where it has 11,000 troops stationed. But Bahrain, aligned with Riyadh, hosts the US Fifth Fleet.

Offering to help broker a peace between the Gulf neighbours, US Secretary of State Rex Tillerson cast the row as a "growing list of irritants in the region" which he said "have now bubbled up to a level that countries decided they needed to take action in an effort to have those differences addressed".

In what seemed like a gesture to Doha, the US military said it had "no plans to change our posture in Qatar". And the US ambassador to Qatar, Dana Shell Smith, tweeted statements endorsing Qatar's campaign to counter local funding for terrorism – which sparked one of Riyadh's key complaints against Doha.

But while it is deeply entwined with the US military establishment, Qatar also irked Washington in the aftermath of the Arab Spring in particular by hosting officials of the Egyptian Muslim Brotherhood, which is outlawed in Saudi Arabia; the Palestinian Hamas movement and the Afghan Taliban, both of which are designated as terrorists by the US; it has close economic ties to Iran, now in Trump's crosshairs; just to be perverse, it maintains relations and does business with Israel; and despite having good relations with Tehran, it is fighting Iran's allies in Syria and in Yemen.

Qatar's self-appointed role as chaperone to Muslim Brotherhood movements during and after the Arab Spring, especially to Egypt's now deposed president Mohamed Morsi, was seen in some quarters as a rare moment of realpolitik in the region. But to Riyadh, it was a too-cocky little neighbour becoming a regional upstart.

Reports from Baghdad and Doha earlier this year were a remarkable revelation of Qatar's uncanny ability to work the region's back channels to achieve remarkable – and dubious – outcomes.

The saga began in Iraq in December 2015, when a hunting party of 26, said to include members of the Qatari royal family, were kidnapped in Shiite-dominated southern Iraq, near the Saudi border. Their release, in April, was part of an extraordinary, regionwide negotiation brokered by Doha and Tehran that included the release of prisoners and the evacuation of civilians to relative safety in the Syrian civil war.

Qatar reportedly sweetened the deal by handing over big bags said to contain millions of dollars, which were then divvied up between the kidnappers and the Syrian fighting factions.

That annoyed Iraq and the Saudis, but the straw that broke the camel's back came days after Donald Trump's May visit to Riyadh, when comments attributed to Qatar's ruler, Sheikh Tamim bin Hamad al-Thani, appeared on the website of Doha's official news agency - the result of hacking, the Qataris insisted - criticising Trump's Iran policy and cautioning that Trump might not be President for long.

Backed so enthusiastically by Trump, the Saudis believe themselves to be in the driver's seat. But it remains to be seen if the Qatari princes can or will swallow Riyadh's laundry list of demands: break its ties with Iran; dispatch the Brotherhood and other Islamist movements, whose officials it hosts; and clip al-Jazeera's wings.