A breach between Qatar and some of its Gulf neighbours is a pivotal test for a three-decade-old union formed to stand united when threatened by common enemies.

The six neighbours have struggled for years to transform their alliance from a simple security pact into an integrated economy. But plans for a customs union, integated power grids and a joint military command remain unfinished or unrealised.

Critics of the Gulf Cooperation Council (GCC) blame its inadequacies on petty jealousies, border disputes, or the perceived dominance of its biggest member, Saudi Arabia.

If the allies can no longer reach broad agreement on how to navigate the political troubles afflicting the region, then the main point of their partnership is in question, say analysts.

The GCC, which also includes Kuwait, Bahrain, the UAE and Oman, has managed to present a united front at times of threat ranging from Iranian revolution to Iraqi invasion.

Even as most Gulf economies are booming and the GCC touts itself as a rare outpost of stability in a turbulent region, the member countries have never appeared more divided.

"Will the GCC kill itself?" ran Thursday's headline in Kuwaiti newspaper Al-Rai.

Wednesday's statement by Saudi Arabia, the UAE and Bahrain that they were withdrawing ambassadors from Doha and all but accusing Qatar of undermining their internal stability was unprecedented as a public display of divisions.

BROTHERHOOD

Saudi Arabia and the UAE are incensed by Qatar's support for the Muslim Brotherhood, which they regard as a dangerous political enemy. They are also cross about Doha's backing for more radical Islamist groups in Syria.

The UAE summoned the Qatari ambassador in February after Qatar-based Brotherhood cleric Youssef al-Qaradawi condemned the UAE as against Islamic rule, a remark the UAE described as insulting and shameful.

UAE media quoted Qatari Foreign Minister Khaled al-Attiyah as saying the comments did not reflect Qatar's views. Sources close to the cleric said he would not stop speaking his mind.

Saudi Arabia and Qatar are leading backers of rival Syrian rebel groups, and they and other Gulf states are the principal external forces supporting key players in Egypt and Yemen.

Acting together they could effect regional change. Apart, they risk dragging the Gulf into a quagmire.

There have been plenty of previous rifts among the six states, but they have never made such public airing of problems.

Gulf citizens see their region as the last bastion of security in the Arab world, with Iraq and Syria in conflict, Yemen and Libya in chaos, Egypt destabilised and Lebanon and Jordan undermined by turmoil in neighbouring states.

Saudi Arabia and Qatar in particular have had a series of disputes, including border clashes in 1992 that led to several deaths and a five-year period from 2002 when Riyadh had no ambassador in Doha after arguments about Al-Jazeera broadcasts.

For Saudi Arabia in particular, the disunity is a source of frustration. Riyadh has pushed hard since late 2011 for the GCC to forge a closer union on a shared foreign and security policy.

The personal initiative of King Abdullah, the idea emerged as a response to the Arab Spring and fears of Iranian interference and represents an important building block of Saudi efforts to become less dependent on the West.

"The Saudis are strongly committed to the unity of the Gulf states, and they want other states to take their share of responsibilities towards the people of the Gulf," said Saud Al-Sarhan, director of research at the King Faisal Center for Research and Islamic Studies in Riyadh.

"Saudi Arabia is taking control of regional and Arab security, and slowly bringing to an end the era of reliance on foreign partners for strategic priorities," he added.  - Reuters