Despite spending billions on American manufactured anti-missile platforms, the Arab Gulf states have yet to agree on building a unified umbrella and joint early warning system which Washington has long argued is the best means of defense against an Iranian attack.

The secretary general of the Gulf Cooperation Council, to which the six Sunni monarchies of the region belong, Abdul Latif Bin Rashid Al Zayani, urged the development of a joint missile defense system last month. Such a shield, he said, could be “backed by the United States and Western allies.”

However, the six countries remain uneasy about sharing data, Reuters reports. Nor can they decide on the location of a central command.

Saudi Arabia, the second largest oil exporter in the world and a key American ally in the Middle East, is by far the most populous and powerful member of the GCC. Its neighbors, the United Arab Emirates in particular, are uneasy about the kingdom’s domineering role. Saudi Arabia already hosts the GCC headquarters and is home to the Peninsula Shield, a joint defense force set up in 1986 which was most recently deployed in Bahrain when demonstrations erupted against the ruling Al Khalifa there last spring.

The emirates pulled out of a planned monetary union among the GCC states in 2009 after Saudi Arabia was voted as the host of a common central bank.

The Gulf states share a mistrust of Iran’s nuclear intentions and seek to contain its regional influence. The joint military intervention in Bahrain last year was inspired by fears of Iranian involvement in the island nation’s Shia uprising. Iran is among few Shia majority countries in the Muslim world. The Arab Gulf states are all ruled by Sunnis.

A pan-Gulf defense shield would likely be supervised by the Americans which is another reason for skepticism on the part of Arab states. The United States would like to integrate an early warning system with their navy ships deployed in the Persian Gulf but allies, including Saudi Arabia, are hesitant to surrender control of such a system.

In the absence of a joint missile shield, the United Arab Emirates in December spent $3.6 billion to buy Lockheed Martin’s Theater High Altitude Area Defense to protect their cities and oil installations. The system is designed to destroy short- and intermediate range ballistic missiles both inside and outside the planet’s atmosphere.