In the past day, countries including Saudi Arabia, Egypt, the United Arab Emirates, Bahrain and the Maldives have cut ties with Qatar, citing terrorism concerns. The severance in relations affects air transport, trade and — more crucially for the U.S. — efforts to unify Arab allies.

Qatar is host to the U.S. Central Command's regional headquarters, and hosts a key air base for the U.S.-led coalition against the Islamic State. It remains unclear how or if coalition members that have severed ties with Qatar will continue to participate in the operations out of that base.

Saudi Arabia, the UAE and Bahrain have banned Qatari flights from their airports and airspace. They've ordered Qatari diplomats to leave in 48 hours and other Qatari nationals to pack up in two weeks. And Saudi Arabia is shutting its border with Qatar.

The cutoff in relations was sparked by a purported hack into Qatar's state news agency and leaks of alleged comments by the Qatari Emir Tamim bin Hamad al-Thani in support of the Muslim Brotherhood and Saudi Arabia's arch-rival, Iran.

The diplomatic row follows President Trump's visit to Saudi Arabia two weeks ago — his first trip abroad as president, where he convened a summit of Arab and Muslim allies. The meeting aimed to gather those states into one camp to counter Iran and ISIS.

It appears Saudi Arabia is now working to consolidate its position as the leader of that group and sideline Qatar, whose policies have often been at odds with other members of the Gulf Cooperation Council, a regional alliance of six nations.

In a statement, Qatar's foreign affairs ministry "expressed deep regret over the decision of Saudi Arabia, the United Arab Emirates and the Kingdom of Bahrain to close their borders and airspace and cut off diplomatic relations. Such measures are unjustified and are based on baseless and unfounded allegations.

"Qatar has been exposed to an instigation campaign based on allegations that amounted to absolute fabrications, which proves that there are premeditated intentions to cause damage to the State."

Secretary of State Rex Tillerson quickly offered his help to mediate the rift, calling on the GCC to maintain unity. He expressed confidence that the growing crisis would not affect military efforts against ISIS.

"I do not expect that this will have any significant impact, if any impact at all, on the unified fight against terrorism in the region or globally," he told reporters while on a visit to Australia.

"I think what we're witnessing," Tillerson said, "is a growing list of some irritants in the region that have been there for some time, and obviously they have now bubbled up to a level that countries decided they needed to take action in an effort to have those differences addressed."

A similar diplomatic spat erupted in 2014, in which diplomats from various Gulf countries were withdrawn from Qatar but air links and borders remained open.

Saudi Arabia, Egypt and other Arab states blame Qatar for supporting the Muslim Brotherhood and other groups in the region, and they view the state-owned, Doha-based satellite channel Al-Jazeera as a mouthpiece for Islamists who challenge their governments.

On Monday, Saudi Arabia shut down the Qatari broadcaster in its territory and took it off the air.

Gulf analyst David Roberts, an assistant professor at King's College London and the author of Qatar: Securing the Global Ambitions of a City-State, says whether or not the alleged comments that led to the current rift are true, "These comments attributed to Emir Tamim effectively voiced all the policies and issues that everyone thought Qatar was doing anyway."

Qatar and the countries that have broken relations with it have "a fundamental clashing [of] opinions of how to operate or with whom you should operate. The UAE's approach to foreign policy, where possible, is always seek to work with a nationalist-oriented group, as opposed to Islamist," Roberts says. "Qatar, more often than not, seems to forge its relationships along Islamist lines."

But the bottom line, Roberts notes, is "there's been a feeling for decades that Qatar is an individually focused state doing what it wants to do, and hasn't paid enough attention to GCC security issues. The crux is that the UAE, Bahrain and Saudi Arabia think that Qatar has made their security situation and regional stability worse."

He tells NPR it is not entirely clear why longstanding issues have boiled over now, but notes, "We can't ignore the fact that Donald Trump was in the region not too long ago, which really empowered Saudi Arabia and the UAE. They feel they have a certain carte blanche to push their agenda."

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