US forges its own alternative to Law of Sea Treaty

The Reagan administration is drafting a presidential proclamation that would claim for the United States almost all fish, minerals, and other natural resources in a 200-mile-wide swath of sea off US coasts.

Establishment of such a coastal economic zone would back up US rejection of the United Nations Law of the Sea Treaty, which opens for signature in Jamaica early next month. Government officials say the draft proclamation, linked with companion legislation proposed by Rep. John B. Breaux (D) of Louisiana, is another step in the campaign to persuade its allies such as West Germany to also abstain from signing the LOS.

These steps are ''designed to be our nation's answer to the $64,000 question: What do you do if you don't sign the Law of the Sea?'' says a congressional source.

Current US offshore claims stem from 1945, when President Truman declared that the US had exclusive rights to exploit the resources of the continental shelf, and to control fishing in waters up to 200 miles off domestic coasts.

The Cabinet Council on Natural Resources is now considering various drafts of a proclamation that would extend the claim for all resources (except migratory tuna) to 200 miles, executive branch officials say, putting an additional 6 million square nautical miles of ocean under the economic control of the US. The US would also still dominate those spots where the continental shelf pokes out beyond 200 miles.

Any proclamation by President Reagan would likely be a short document outlining general policy. Congress would have to follow along behind, and pass legislation filling in the details.

Though not designed by the White House, legislation that could fill such a role was introduced earlier this year by Representative Breaux. The bill would establish a 200-mile economic zone, precisely define the limits of the US continental shelf, and set procedures governing scientific research in US coastal waters. Among other things, it calls for a presidential proclamation similar to the one now being considered by the White House.

Aides to Breaux characterize the bill as ''largely a discussion document'' that will be refined in the next Congress.

The bill is similar to the UN Law of the Sea Treaty section that guarantees coastal states a 200-mile economic zone, though there are some crucial differences in the areas of research and migratory fish. The Breaux bill also has a more liberal definition of ''outer continental shelf'' than the Law of the Sea Treaty.

''We're trying to send a signal, giving other nations a chance to see there are other things beyond the Law of the Sea,'' says a Breaux aide.

After eight years and millions of diplomat-hours, the sweeping Law of the Sea Treaty will finally be open for signature Dec. 6 in Jamaica. The Reagan administration, objecting to some provisions governing seabed mining procedures, such as a section guaranteeing third world nations access to US technology, refuses to sign.

State Department envoy Donald Rumsfeld has been shuttling to other industrial democracies, hoping to persuade them to refrain from becoming a party to the treaty. He has had little success. It did not help that his schedule took him to two important nations, Japan and West Germany, just as their governments were changing, according to a Washington source.

Though it won't sign the treaty itself, the US will sign the final act of the conference, says a State Department official. This is a ''formality'' indicating the US participated in the drafting process, says the official.

Signing the final act also entitles the US to send a nonvoting observer to the preparatory commission that will draft seabed mining rules. The US won't avail itself of this opportunity.

''There's no point,'' argues the State Department official. ''It would send other nations the wrong signal.''

Others say the US will miss a valuable chance to comment on the seabed mining rules.

''Observers can participate fully in all deliberations,'' says Lee Kimball, executive director of Citizens for Ocean Law.

Though the US ''can't fix everything,'' she says, it could use observer status to make the seabed mining rules significantly more palatable.