Despite massive spending on Western weapons, the Arab monarchies of the Persian Gulf are "unable to secure themselves from any external threat" -- meaning Iran -- and are running up huge public and foreign debt, a Gulf think tank says.

Omar al-Shehabi, director of the Gulf Center for Development Policies in Kuwait, said that even though the defense expenditure of the six Gulf Cooperation Council states is the highest in the world, exceeding the combined military spending of Israel and Britain, they still have to "rely on Western countries to provide military protection and security."

The GCC states -- Saudi Arabia, the United Arab Emirates, Kuwait, Qatar, Bahrain and Oman -- have spent hundreds of billions of dollars on weapons and military equipment from the United States and Europe over the last three decades.

Right now, the report said, there are 50,000 U.S. military personnel deployed in the oil-rich Gulf, where the U.S. 5th Fleet is headquartered in the island kingdom of Bahrain. That's about the same number of U.S. troops based in Germany and exceeds the size of the U.S. force in Japan. This, the report observed, is a consequence of the "chronic security imbalances in the region."

Shehabi argued, as the United States has for many years, that collective security by the Gulf states themselves is the only way to provide adequate defense security.

"Otherwise the small size and population of the GCC states will always leave them vulnerable and require them to align themselves with larger powers in the region or the world."

Shehabi added: "The puzzling question that needs more in-depth research, however, is why the Gulf failed to build up adequate military self-sufficiency, given the huge amount of money that is being spent annually in military expenditure. This needs more research and honest self-reflection."

This lack of a coordinated defense strategy, much talked about but largely unrealized by the GCC members, stems in large part from historical rivalries between the tribal dynasties of desert sheikdoms.

There is also significant resentment among the smaller states about domination by Saudis, the GCC's superpower.

"The security shortcomings in the GCC coincide with shortcomings that are no less important, which is the imbalance of population that is reflected in the increasing reliance on expatriates, the study said.

It emphasizes the long-running question of the effectiveness of the GCC's military spending.

The Center for Strategic and International Studies in Washington has observed that the vast outlay by the GCC countries, particularly Saudi Arabia and the United Arab Emirates, has not provided the unity and focus on integrated defense and the key missions needed to create effective forces, deterrence or balanced war-fighting capabilities.

Still, all of this has provided U.S., French and British defense companies with major contracts at a time when they're all suffering from severe cuts in domestic defense budgets.

Russia's been seeking to break into the lucrative GCC market, but has not really made a major impact. It's unlikely to now since it's backing the Syrian regime of President Bashar Assad, which Saudi Arabia and Qatar are striving to topple.

Despite the Syrian conflict and other crises across the region, in terms of military spending Saudi Arabia and the gulf states are still primarily focused on the region's main threat: Iran.

Saudi Arabia, the only Middle Eastern power among the world's Top 10 military spenders, forked out about $48.5 billion on defense in 2011.

In 2012, it signed a $3 billion deal for an additional 30 Hawk jet trainers/light attack aircraft from BAE Systems of Britain.

Riyadh's currently negotiating with Germany for as many as 600 Leopard 2A7+ main battle tanks made by Krauss-Maffei Wegmann and Rheinmetall worth about $12.6 billion.

According to the CSIS, forecasts for defense spending by Saudi Arabia are $49.1 billion in 2013 and $50.1 billion in 2014.

The Emirates, which has invested heavily for several years on missile defense and air power, is expected to spend $7.52 billion this year and $7.77 billion in 2014.

Abu Dhabi acquired two of Raytheon's Terminal High Altitude Area Defense missile defense system for more than $7 billion.

But even as defense spending remains high, there's still little sign of a coordinated Gulf-wide defense system, including the integrated early warning system the Americans have been advocating for years.