The Pentagon is about to announce new plan for combating the Soviets at sea, including putting more U.S. airpower in Iceland and wiring Key West, Fla., for joint Air Force-Navy exercises in ocean warfare, defense officials said yesterday.

The idea is to bridge the historic gap between Air Force and Navy roles when it comes to fighting at sea in the belief the Soviet threat has become too large for either service to handle by itself.

Defense officials said impetus for formalizing Air Force-Navy cooperative efforts into a policy document came from Defense Secretary Caspar W. Weinberger and civilian and military leaders of both services.

Added thrust came from the battle of the Falkland Islands where Argentina demonstrated how land-based airplanes armed with "smart" missiles can sink modern warships, Pentagon leaders se a similar role for U.S. heavy bombers, the B52 and B1, armed with anti-ship missiles.

The new policy document, according to those who worked on it, also reflects the growing conviction of strategists that technocrats at consoles in lumbering airplanes will often decide whose ships are sunk and whose planes are shot down in tomorrow's battles.

The Air Force technocrats who warn of attacking planes and guide combat pilots to their quarries by radioed instructions fly in converted Boeing 707 passenger liners called AWACS, for airborne warning and control system. Their Navy counterparts fly in Grumman E2C Hawkeyes, a plane Israel used recently in sweeping the skies clean of Syrian aircraft over Lebanon.

Under the new policy, the Air Force would put more AWACS over the world's oceans and practice working in conjunction with the electronic eyes and ears of the Navy Hawkeyes. Air Force and Navy technicians would fly in each other's airplanes as part of this integration effort, officials said.

"By putting out the AWACS and E2C together," enthused one Navy official, "we can see what's coming for 600 miles around."

The sooner a surface ship knows an aircraft is on the way the bigger chance it has of surviving an attack. Soviet long-range Backfire bombers are considered the biggest aerial threat to U.S. surface ships. The Navy defense against them is three-tiered.

First, Navy fighter planes flying from carriers would try to knock down the Backfire before it could launch its cruise missiles; second, the ship would fire its missiles at any cruise missiles that were launched, and third, the ship's fast-firing battery, called Phalanx, would fill the air with lead around the ship in hopes of stopping any missiles that penetrated the outer defenses. To give the United States and other North Atlantic Treaty Organization nations more warning time and firepower over the North Atlantic and Norwegian Sea, the Pentagon's plan calls for doubling the number of AWACS based in *iceland from two to four and replacing the 12 Air Force F4E fighter planes there with more sophisticated Air Force F15s.

The F15s eventually will be equipped with so-called conformal fuel tanks, enabling them to fly 675 miles from Iceland to patrol the Norwegian Sea and return without refueling in midair. This is twice the combat radius of the F4Es now in Iceland. Such long range might enable Air Force planes to fly from land to help protect Navy carriers.

A less dramatic but no less important policy change, officials said, will be installing gear needed to enable Air Force planes and Navy planes and ships to communicate with each other. "We can talk to other nation's navies better than we can our own Air Force," Navy Secretary John F. Lehman Jr. has complained in pressing for compatibility.

Advanced radars and communications would be installed at the Navy base at Key West for the Air Force and Navy to practice sea warfare tactics together off Florida. Melding land-based and sea-based Air Force and Navy skills for finding and destroyling ships, submarines and aircraft is the objective here. It would cost more than $25 million to install the radars and other gear needed for such exercises, Navy officials say.

One old hand at the Pentagon recalled ruefully yesterday that the Air Force got the high-elbows treatment from the Navy and its congressional sympathizers back in the early 1970s when a Defense Department plan to arm B52s with anti-ship missiles was killed by Congress. Lehman is telling associates that he and Air Force Secretary Verne Orr, as well as the military leaders of each service, are on the same wave length this time.