Saudi Arabia and other oil-rich monarchies, already rattled by the turmoil unleashed by the 2011 Arab Spring, fear a landmark nuclear agreement reached last month could herald a wider rapprochement between the West and their regional rival Iran.
But a proposal to develop the Gulf Cooperation Council into a fully-fledged union has proven divisive, with Oman threatening to leave the GCC if the idea is approved. The group also includes Saudi Arabia, Kuwait, Qatar, Bahrain and the United Arab Emirates.
The summit comes a week after Iranian Foreign Minister Mohammad Javad Zarif visited four GCC states to reassure them over the interim nuclear agreement, which would freeze some of Iran's nuclear activities in exchange for some sanctions relief.
Relations with Iran "are entering a new space different from the past. A space that is extremely positive and constructive," Kuwait's foreign ministry undersecretary Khaled al-Jarallah told reporters after Zarif's visit.
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"Iran is trying to exploit the momentum generated from the nuclear deal and Saudi Arabia is trying to repulse this push," Saudi political analyst Khaled al-Dakhil told AFP.
"Tehran is trying to create a wedge between Saudi Arabia and some GCC states like Oman and Qatar."
Saudi Arabia, which cautiously welcomed the nuclear deal, is engaged in an increasingly sectarian proxy war with Iran in Syria, where Riyadh backs the Sunni-led rebels and Tehran is a key ally of President Bashar al-Assad's embattled regime.
The Gulf leaders are also expected to discuss Egypt, where Saudi Arabia, the UAE and Kuwait strongly backed the July 3 military overthrow of Islamist president Mohamed Morsi, whose government was seen as close to Qatar.