Saudi Arabia has threatened to blockade its neighbouring Gulf State Qatar by land and sea unless it cuts ties with the Muslim Brotherhood, closes Al Jazeera, and expels local branches of two prestigious U.S. think tanks, the Brookings Doha Center and the Rand Qatar Policy Institute.

The threats against the television station Al Jazeera, Brookings Institute and the Rand Corporation, were made by the Saudi Foreign Minister Saud bin Faisal in a foreign minister's meeting of the Gulf Cooperation Council in Riyadh last week, according to a source who was present. Bin Faisal said only these acts would be sufficient if Qatar wanted to avoid "being punished."

News of the threats to shut down the Brookings and Rand Corporation think tanks in Doha will embarrass the U.S. president Barack Obama, who is due to visit Riyadh at the end of month. His Secretary of Commerce Penny Pritzker was in Abu Dhabi on Sunday, where she told AP that she will tell officials from the United Arab Emirates, Saudi Arabia and Qatar that closer economic cooperation with Washington is a bridge to building deeper security ties.

The Saudi royal family were enraged and threatened, in equal measure, by the role Al Jazeera played in the first years of the Arab Spring , which saw fellow potentates deposed in popular revolutions in Tunisia and Egypt . They are now equally upset at the sympathetic coverage the Doha-based television station gives to the opposition, secular and Islamist, in Egypt. Three journalists from Al Jazeera, its Egypt bureau chief Mohamed Fahmy the Australian correspondent Peter Greste and Egyptian producer Baher Mohamed appeared in court in Cairo last week accused of "joining a terrorist group, aiding a terrorist group, and endangering national security." A fourth journalist, from Al Jazeera Arabic, Abdullah al-Shami is being tried in a separate case.

The military backed government in Egypt accuse Al Jazeera of providing a platform for the supporters of the ousted president Mohamed Morsi, and the now outlawed Muslim Brotherhood. "Journalists are not terrorists," Fahmy shouted from the cage in the courtroom.

The threat to lay siege to Qatar was made in private before the Kingdom withdrew its ambassador to Doha and issued a decree on Friday declaring the Brotherhood a terrorist organization, alongside Al Qaeda, Hezbollah, the Islamic State of Iraq and Syria and the Nusra Front.

The threat of a sea blockade is not taken seriously in Qatar. But the state's only land border is with Saudi Arabia and is therefore easily closed. At present a substantial amount of the fresh food and goods the bustling city of Doha needs every day passes through this border. There are only 40 miles of sea and land borders between the two states, and clashes have taken place along them in the past. The border was disputed for 35 years. Qatar and Saudi Arabia skirmished in 1992, when Saudi troops occupied a border post. A final border agreement was only signed in 2001.

The increasingly McCarthyite tone adopted by the Saudi monarchy in its public pronouncements about the Brotherhood is thought to be a sign of desperation at the way events in Egypt are turning out. Supporting the military dictatorship in Cairo is costing the kingdom and its ally in the United Arab Emirates dear. Together they have spent $32 billion propping the coup up, with no end in sight to the chaos.

The Egyptian authorities are battling continuing protests by Morsi supporters and secular activists, a mass campaign of civil disobedience including attacks against policemen and police stations, strikes, an insurgency in the Sinai peninsula, as well as drive by shootings and bomb attacks mounted by Islamic militants.In hinting that he would run for the presidency, General Abdel Fatah al-Sisi said his country needed 3 trillion Egyptian Pounds, twice the current public debt to refill the nation's empty coffers.

The draconian decree issued on Friday will have a dramatic impact on free expression in Saudi Arabia itself. Cast in the most general terms, it targets not only supporters of named banned organizations, but anyone "preaching any atheistic thought." It bans all protest and anyone attending conferences or symposia, locally or internationally "that target the security or stability of the country and stir up sedition within society."

Article four of the decree outlaws: "whoever manifests affiliation to any of these [groups] or expresses sympathy with any of them or promotes any of them or convenes meetings under their umbrella whether inside or outside the Kingdom."

The articles continues: "This includes participating in all forms of media, whether audio or print or video, and in social media networks of all forms and types, audio, print and video, and in internet websites by reporting or re-transmitting any of their contents in whatever format, or the use of the slogans or emblems of these groups and currents or the use of any such symbols that may express support for them or sympathy with them."

This is aimed at the millions of twitter accounts in the Kingdom, which has become the only unfettered means of expressing opinion and dissent.

Analysts elsewhere in the Gulf expect the Saudi tactics to backfire. They have already paralyzed the Gulf Cooperation Council, with Oman refusing to expel Qatar and Kuwait deeply uneasy. It is also propelling the start of a significant regional realignment. Within hours of the Saudi decision to withdraw its ambassador to Doha, the Turkish prime minister Recep Tayyip Erdoğan called the emir of Qatar Sheikh Tamim bin Hamad in support. Doha has also become closer to Iran as a result of its bust up with Riyadh.

The open diplomatic warfare between Riyadh and Doha pits two generations of Gulf ruler against each other -- the 89-year-old Abdullah bin Abdulaziz versus the 33-year-old Tamim bin Hamad. It will be interesting to see which generation prevails.