Royal Navy steams for the South Atlantic; Logistics hamper British effort to reclaim territory

As it steams from Portsmouth, England, toward the Falkland Islands 8,000 miles away, Britain's Royal Navy presents two pictures.

It is vastly superior to the Argentinian force it expects to encounter in about two weeks. But it faces severe logistical problems that will hamper any effort to retake the remote islands claimed by both countries. The fact that Britain had earlier decided to reduce the size of what was once the world's mightiest navy also is much in evidence as the force of nearly 36 ships heads for the open Atlantic.

For this reason, say US military and intelligence experts, the British are likely to press for a diplomatic resolution while flexing their naval muscle en route to and upon arrival at the Falklands. Next could come a barricading of the islands to isolate the Argentinian force now there, and perhaps the landing of British marines on one of the smaller islands as a token recapturing of British soil.

Only if those efforts fail, analysts here suggest, are the British likely to take stronger military action against Argentina.

British officials have said they will do whatever they think necessary to reclaim the Falklands. They have not ruled out anything, including the use of their sturdy submarine force (28 attack subs, 12 of which are nuclear). With some 4,000 Argentine troops already in the Falklands, however, this poses a hostage-like situation for the 1,800 islanders (97 percent of whom are British).

''I find it hard to believe they're going to war,'' says retired Adm. Stansfield Turner, former director of the US Central Intelligence Agency.

Pentagon spokesman Comdr. Jeffrey Renk notes the ''long logistics chain'' between the Falklands and the nearest point at which the British ships likely would be able to resupply. These are the Ascension Islands, still about 3,500 miles from the Falklands.

And with at least two weeks before the British fleet arrives, says Commander Renk, Argentina could add substantially to the invasion force already in place. According to the International Institute for Strategic Studies in London, Argentina has an army of 130,000 men and a navy of 36,000, including marines.

If Britain wants to assume command of the seas around its beleagured colony, however, it should be able to do so quickly.

Argentina has just four submarines, two of which were commissioned in 1945. Its lone aircraft carrier was built the same year.

Britain is sending two carriers south (one of which is just two years old), armed with attack antisubmarine helicopters and vertical-takeoff jets. Included in the fleet are guided-missile destroyers, frigates, an amphibious assault ship with 5,000 men, and various support ships.

Britain's submarines are ''almost totally invulnerable,'' says Admiral Turner , and ''could pick off the whole Argentinian fleet in nothing flat.''

But such an opening gambit by the British is thought unlikely, leaving the more difficult option of establishing and -- more important -- maintaining a credible military presence while the diplomatic maneuvering continues. In this case, time is an advantage to Argentina, since the British fleet's principal source of fuel, ammunition, and other supplies is one-third of the way around the globe.

As for a British attack on the South American continent, US experts think this unlikely unless the Royal fleet is directly threatened from the mainland. Given the relatively small size of the Argentinian Air Force and distance from the Falklands, such a threat does not seem imminent.