Buoyed by its enhanced leadership role in the Islamic nation's organization, Saudi Arabia is reaching out to assert power in the Persian Gulf where the debilitating Iranian-Iraqi war has deepened the sense of a power vacuum.

The foreign ministers of six Arab sheikdoms and kingdoms -- Saudi Arabia, Kuwait, Qatar, Bahrain, Oman and the United Arab Emirates -- met here earlier this month and laid plans for a Gulf Cooperation Council that some hope will lead to a pact aimed at protecting the vital oil-exporting region and keeping out foreign powers.

The meeting came only days after Saudi Arabia hosted leaders of 38 Moslem nations who unanimously asserted that the security, peace and stability of the gulf is the "exclusive responsibility" of the nations in the region.

But conflicting notions among participants about the ultimate objectives of the embryonic council, plus the absence from the meeting of Iraq -- militarily the most powerful Arab gulf state -- have already raised serious questions about the ability of the sheikdoms and kingdoms alone to shoulder such a burden.

Furthermore, none of the six countries has more than a symbolic navy or a small air and land force, casting grave doubts on even their combined military ability to play the role of guardian over the Western world's vital oil lanes through the gulf.

Experts of the six plan to meet again in Muscat next month to work out the details of their council and prepare for a subsequent summit to formally launch the program. By that time, it may become clearer whether the scheme holds any potential for establishing a credible gulf security system or will simply limit itself to the coordination of economic and other policies.

For the moment, the six constituent members of the council are playing down the idea of a gulf defense pact, reportedly partly out of fear of provoking Iran. Another reason, however, is their obvious differences about what military ties, if any, they should maintain with the Western powers.

Two of the six, Oman and Bahrain, already are providing the United States military with facilities, the former having signed an access agreement for the Rapid Deployment Force and the latter a commerical port accord for the Navy's Middle East Force.

The other four, however, have eschewed such public ties. Several, including Saudi Arabia, have repeatedly denounced the idea of providing bases, or facilities, in the gulf to U.S. or any other outside forces. The Saudi foreign minister, Prince Saud, describes Western, particularly American, bases and facilities as "lightning rods" serving only to provoke the Soviets into obtaining equivalent rights in the region and thus accelerating the two superpowers' race for influence in the gulf.

Saudi Arabia reflects amply all the ambiguities of policy and attitudes shared by the other Arab gulf states outside Iraq. The oil and financial powerhouse of the region, it has, nonethelss, found itself just a vulnerable as the smaller sheikdoms to the new pressures generated throughout the region by the Iranian fundamentalist Moslem revolution, the Soviet occupation in nearby Afghanistan and the U.S. Rapid Deployment Force.

Under pressure as well from Iraq, which wants to eliminate all superpower influence from the gulf, the kingdom has sought to reaffirm its security by taking its distance -- particularly in public -- from the United States while casting about for some Islamic or regional grouping capable of offering protection from the renewed Soviet-American cold war closing in on the region.

The shortcomings of such a policy were made embarrassingly clear last fall when the Saudis, suddenly fearing an Iranian attack on their oil installations, called on Washington to rush early-warning AWAC radar planes to the kingdom to help protect them.

This public recognition of their continuing reliance on U.S. military protection did not prevent King Khalid, however, from calling last month on all Moslem states to forego military alliances with East or West and avoid seeking protection under the umbrella of a superpower.

"Security comes from placing our confidence in God and in ourselves," he told the Islamic summit conference.

The underlying ambiguity in the Saudi position is not likely to disappear in the near future. The kingdom remains extremely dependent on foreign, particularly American and Pakistani, assistance to train and maintain its armed forces.

While American press reports of an entire Pakistani division coming here are apparently false, informed sources here report a 600-man engineering battaliion in building roads and military installations and perhaps 2,000 Pakistanis are serving as advisers and thousands of others in menial and manual labor jobs in all branches of the armed forces.

The United States, for its part, has since 1953 maintained a large military training mission here. It presently numbers about 400 advisers and related personnel who are involved at all levels of the Saudi military establishment. Meanwhile, the U.S. Corps of Engineers is responsible for managing contracts on behalf of the Ministry of Defense and the separate Saudi National Guard. Altogether, several thousand of the 45,000 Americans living here are associated in one way or another with the training and expansion of all branches of the Saudi armed forces.

The primary American military connection, while increasingly being challenged by France and other European states, is still so strong that one informed source commented about past efforts of the Carter administration to obtain facilities here: "Frankly, we don't need any bases in the kingdom; they are already here. If they [the Saudis] needed us badly enough, they will become available to us."

Such an invisible American backup, whether it be "over the horizon" in the Indian Ocean or based in the United States, appears to be the closest kind of cooperation with the United States the Saudis can presently afford politically.

This has become increasingly true, according to Western diplomats here, as Saudi Arabia moves closer to Iraq, whose drive to eliminate all traces of Western or Eastern military presence from the gulf and substitue an Iraqi-dominated Arab force presents an additional challenge to Saudi diplomacy.

The precise reason for Iraq's absence from the founding meeting of the Gulf Cooperation Council is not altogether clear, but given the Iraqi drive for preeminence in the region it did not go unnoticed.

Some Western analysts said both Iraq and the other Arab gulf states were concerned lest the council be viewed by Iranians as an Arab defense pact aimed against them, making the search for a peaceful resolution in the Persian Gulf war and any Arab mediation even more difficult.

But others saw in Iraq's conspicuous absence the desire of the gulf sheikdoms and kingdoms, which share little in common politically with the Iraqi lay and socialist state, to develop their own grouping as a counterweight to their bigger brother to the north as well to the East and West.