By William Maclean and Amena Bakr
DUBAI/DOHA (Reuters) - Gulf Arab states have shelved a bitter row among themselves, hoping to repair an alliance that has been sorely tested by chaos in the Middle East and the prospect of an Iranian nuclear deal that could tilt the regional balance of power toward their old foe Tehran.
Saudi Arabia, the United Arab Emirates (UAE) and Bahrain agreed at a meeting on Sunday to return their ambassadors to Qatar, signaling an end to an eight-month dispute over Doha's backing of Islamist militants in Syria and elsewhere and its promotion of Arab Spring revolts.
An official photograph showed Qatar's youthful emir, Sheikh Tamim bin Hamad al-Thani, kissing the head of Saudi King Abdullah, who is over 90, in reconciliation at the meeting of Gulf Arab rulers in Riyadh. The king was the driving force behind the closing of ranks, analysts and a diplomat said.
Saudi Arabia, Bahrain and the UAE withdrew their envoys in March. They accused Qatar of failing to abide by an agreement not to interfere in one another's internal affairs and not to support the Islamist Muslim Brotherhood, seen as a terrorist group by some Gulf Arab states. Qatar denies that charge.
Officials said the possibility of a thaw in relations between Tehran and the United States, the Gulf States' main ally, following any nuclear accord was a constant preoccupation of Gulf Arab rulers, but was not the immediate cause of Sunday's agreement.
The rulers instead appear to have mended fences for fear the row would otherwise spin out of control, possibly leading to a boycott of the annual summit their six-nation Gulf Cooperation Council (GCC) alliance to be hosted by Qatar next month.
A boycott would have been a deep embarrassment to Qatar, amplifying an impression of GCC disarray and raising doubts about the point of a three-decade-old union of monarchies created to stand together against common adversaries.
BASTION OF STABILITY
Nevertheless the top GCC concern is to protect its members, who see themselves as a rare Arab bastion of security, with Iraq and Syria at war, Yemen and Libya in chaos, Egypt destabilized and Lebanon undermined by the turmoil on its borders.
Referring to the region's difficulties, Kuwaiti Prime Minister Sheikh Jaber al-Mubarak al-Sabah said the accord among Gulf states was important because without it they would be "vulnerable to storms", the state's al-Rai newspaper said on Tuesday.
"GCC disunion was probably deemed as too dangerous by Saudi Arabia and other GCC countries for the stability of the region," said Jean-Marc Rickli, assistant professor at the department of defense at King's College London, based in Doha.
The Gulf's Sunni Muslim dynasties also want to counter Iran, which they regard as an expansionist Shi'ite power bent on exporting its Islamic revolution to the Arab world.
A diplomatic source involved in the reconciliation efforts said that while Iran was not an immediate factor in Sunday's meeting, "the concern over Iran and its nuclear work is always there and has never gone away".
A deal to curb but not scrap Iranian uranium enrichment, which the West says is intended to develop a nuclear bomb, would alarm Israel and Gulf Arab rulers who fear the rise of a regional power hostile to their interests.
Iran and negotiators for six world powers are meeting in Vienna to try to seal an accord by a deadline of Nov 24.
"Even if it is just an interim agreement, it would give a boost to the Iranian posture," said Sami alFaraj, a security adviser to the GCC. "The GCC needed to unify its stances, in light of Iran. Timing is of the essence."
AGREEMENT - BUT FOR HOW LONG?
At Sunday's meeting, King Abdullah secured a fresh pledge from Sheikh Tamim to curb Qatar's support for the Brotherhood and end its media criticism of neighboring Gulf states, a diplomat said. There was no immediate confirmation of that report.
How long the agreement lasts is another question.
Some analysts say its durability is by no means assured, given the depth of Qatar's ties to Islamist groups and its desire to continue to try to play a prominent role in regional affairs.
Alfaraj, the GCC security advisor, said he was cautiously optimistic. But UAE political scientist AbdulKhaleq Abdulla said that while the dispute could be seen as "officially" over, in reality that might not be the case. Qatar had to be given time to show that it was abiding by its commitments, he said.
"It is difficult to know what compromises were reached and how truly satisfied the various parties are," said Emile Hokayem of the International Institute for Strategic Studies.
Rickli said the agreement was probably intended to stop the states intervening in each other's internal affairs. "It is thus likely that we will continue to see different policies when it comes to supporting different actors and groups abroad".
(Additional reporting by Yara Bayoumy and Angus McDowall; Editing by Giles Elgood)