AMERICA IN THE GULF. Navy under the gun. Analysis of naval power: assumed but unproved

``There are serious doubts in the Gulf states about America's willingness to confront Iran,'' says Mazher Hameed, Saudi Arabian author of ``Arabia Imperiled.'' ``This is especially true if the Iranian challenge is of an indirect, passive, or ambiguous nature - as is most likely.'' Whether or not the United States has the political will to prevent or respond to Iranian provocations partly depends on the capabilities of its Navy.

Can it carry out purely defensive escort missions in the Persian Gulf, retaliate credibly if required, and sustain a sizable presence in the area for an undetermined period?

Most experts respond affirmatively - but with qualifications if the operation is of long duration.

The issue really has two facets:

Does the dedication of a sizable force to the Gulf for an undetermined period of time erode overall American war-fighting capabilities?

Can our oceangoing Navy effectively fight the kind of low-level and terrorist threats emanating from Iran in the constrained environment of the Gulf?

The first question was partly resolved earlier in the decade when a permanent naval presence was established in the Indian Ocean, next to the Gulf. This decision involved a diversion of forces from other theaters, and was criticized by many at the time.

``At one time, not having two carriers in the Mediterranean was a heresy,'' according to the former commander of the southern flank of NATO, Adm. Stansfield Turner. Now, frequently only one is deployed there.

The fact is that carrier battle groups and amphibious forces have long been withdrawn from the Mediterranean and the Western Pacific to establish a presence in the Arabian Sea and Persian Gulf area.

But even so, today's numbers are unusually high. Besides the normal carrier battle group in the Arabian Sea, the escort fleet for tankers in the Persian Gulf comprises about eight ships - not including a command ship and the likely addition of the USS Guadalcanal, a helicopter carrier, later this month. The battleship Missouri with escorts is expected later this summer.

And according to Gen. Edward Atkeson, former national intelligence officer for general-purpose forces, many more ships will actually be tied up in the Gulf operation for purposes of rotation and repair.

``Overall, we may be talking about a commitment of some 40 to 50 ships to protect the 11 reflagged tankers,'' he says. ``As we have no uncommitted pool of ships to draw upon, we will have to cut back on other missions.''

Despite these considerations, little criticism has been heard decrying the strategic effect on America's war readiness of the current diversion of ships to the Gulf. Naval authorities cite several reasons for this:

According to Admiral Turner, the relatively relaxed state of US-Soviet relations is the primary explanation. In a period of high tensions between the superpowers, Washington would be reluctant to keep carrier groups in the Arabian Sea or Gulf region.

Second, senior military commanders have become accustomed to keeping forces in the area - unlike the situation at the beginning of the decade.

And third, the deployable battle forces of the US Navy have grown from 491 ships in 1981 to 555 last fall, according to a report by the US Joint Chiefs of Staff. More ships provide slightly greater flexibility, even if they are normally committed elsewhere.

In short, most authorities concur that peacetime operations of the current magnitude in the Persian Gulf can be mounted - albeit at a high cost in terms of dedicated ships. And for a reasonable period, this will not degrade overall American strategic potency. Increased superpower tensions would alter this judgment sharply, however.

The capacities of seagoing warships to combat irregular, low-level, or terrorist threats in the confined waters of the Persian Gulf are assumed, but unproved. ``It's like fighting a guerrilla war at sea,'' says an analyst with Gulf Futures, an energy research and planning group focused on the Persian Gulf region.

True, no potential Iranian weapon is beyond the capacity of the Navy to counter - be it missiles, small boats, airplanes, or mines.

But at the same time, several low-intensity threats presented in the Gulf are credible - and a few Iranian successes simply must be expected:

As is painfully clear after the supertanker Bridgeton was hit by a mine, America's mine warfare capability is distressingly meager.

While helicopters can fill a gap, the facts are that the US has three active mine warfare ships, while the Soviets have 358. West Germany, for perspective, has 57.

And so far, the Iranians have not used more sophisticated techniques, such as planting decoy mines to magnify the impact of harassment. They do not possess mines more advanced than the vintage moored, contact-triggered variety encountered thus far.

Were they to obtain such capabilities, the Navy's current difficulties would multiply. The mine problem can and is being solved - but only by the dispatch of helicopters and yet more naval ships to support them.

Long-range land-based torpedoes, not known to have been used by the Iranians, would present additional hazards. While US defenses against missile attacks are in theory adequate, they must work perfectly to do the job. There is little forgiveness, as shown by the attack on the USS Stark.

The Navy's ability to head off a kamikaze small-boat attack assumes an early response to craft, which could conceivably elude radar detection. US units in the Gulf do not include the smaller patrol craft most appropriate for countering this threat.

And land-based unconventional threats such as sabotage in port, tampering with provisions, or kidnapping of personnel are of course present and even likely in the Gulf case.

If a specific, identifiable problem should prove overly troublesome - such as Revolutionary Guards attacks mounted from Farsiyah Island, or the Silkworm missile batteries deployed near the entrance to the Gulf - the source of the problem would presumably be eliminated by use of overwhelming force.

But if Iranian government responsibility for an attack is ambiguous - as Mr. Hameed, the Saudi Arabian author, thinks most likely - will irrevocable proof be required before retaliation?

Or if a friendly victim of an attack is not technically under American protection, will a response be forthcoming?

These questions, of course, are political in nature. They have yet to be answered.

And if such an escalation were to occur, increased international terrorism and heightened restlessness among Shiite minorities in the Arab Gulf states should be anticipated.

The writer was a government official for two decades before becoming a consultant on international affairs.