Oman, one of the West's most secretive, insular and vital allies in the Arab world, began today what one diplomat called its "coming-out party," hosting a summit of six leaders from the Arab states of the Persian Gulf.

The Gulf Cooperation Council -- made up of Saudi Arabia, Kuwait, Bahrain, Qatar, the United Arab Emirates and Oman -- was created in 1981 after the Soviet invasion of Afghanistan, the fall of the shah of Iran and the beginning of the Iranian-Iraqi war.

The escalation of Iraqi attacks on Iran's main oil facility and the frequent search and seizure of gulf shipping by Iran have brought the war to what Omani Foreign Minister Yousef bin Alawi has described as "a critical stage" that "is threatening the interests of states that are not parties to the struggle."

Yet coming into this, its sixth summit, the Gulf Cooperation Council has yet to develop a clear-cut strategy for mutual defense.

Reports vary as to the effectiveness of a joint Gulf Rapid Deployment Force stationed at Hafr al Batin in Saudi Arabia, but it appears to be mainly a headquarters staff, unlikely to reach brigade strength unless an emergency is declared.

Despite the gulf states' desire to defend themselves, western analysts in the region believe that their most likely move in the event of an overt attack would be to call on the United States for assistance.

Since the signing of an "access agreement" with Oman in 1980, the United States has invested more than $300 million in the construction of facilities at four air bases to stockpile supplies and enable U.S. forces to operate out of here if necessary.

Although there is virtually no American military presence here, the threat of quick American retaliation is seen as an essential deterrence to any open attack that the forces of Oman or the other Arab gulf states could not handle.

"The armed forces are prepared against aggression. It is not exaggerated preparedness," Oman's Sultan Qaboos recently told South magazine. "To quote the English: 'If you carry an umbrella, it never rains.' This is our umbrella."

Increasingly, however, the fear among the states of the Gulf Cooperation Council is not direct attack, but sabotage and subversion.

A suicide car-bomb attack in May that nearly killed the emir of Kuwait is still fresh on many minds.

Kuwait, at the northern end of the Persian Gulf, has served as a key transshipment point for goods going to Iraq. There is some suspicion that the attack on its ruler and other violent incidents there during the past two years were aimed at intimidating Kuwait and its neighbors.

"If you intimidate Kuwait," said one well-briefed observer here, "you've intimidated the rest."

The official extent of security cooperation in the area is still small. Some of the gulf states reportedly are concerned about their vulnerability to Saudi domination in such arrangements. According to one informed source here, a mutual defense pact has been held up because Kuwait is reluctant to grant the Saudis rights to pursue subversives into Kuwaiti territory.

There are also serious differences between the gulf states and the Saudis over industrial policy and ill-defined frontiers.

A longstanding border dispute between Oman and Saudi Arabia over oil-rich lands in the interior has heated up recently, with the Omanis actively patrolling their line, according to well-informed observers.

But as one of these observers put it, speaking of the defense pact to be discussed here, "the practical collaboration is more important than the agreements." There is already increasing coordination among the region's police and counterterrorist forces.

"In a region that has known considerable instability, we are prepared against subversion," Qaboos said confidently in the South magazine interview. "It would be irresponsible not to do so."