FOR YEARS AMERICAN negotiators warned that Congress would only foul up the Law of the Sea talks if it went ahead on its own legislation to license deep-seabed mining by American firms. But the LOS conference, while making headway on other ocean issues, has come up dry on seabed mining: Land-based producers of the minerals found under the oceans have sought to restrict competition, and Third Worlders have demanded an unacceptably large share of the rights, revenues and technology of seabed mining, an activity that few countries are currently in a position to conduct.

The result is that, with the LOS conference lagging and the American companies (and consortia) itching to go the administration now supports legislation. Far from fearing that this will upset the LOS talks, it now feels that the sort of law likely to emerge will concentrate the conferees' attention and help the talks along. From what we understand of the two processes (legislative and diplomatic), we agree.

The House bill, already worked over by four committees, is due to come to the floor this week. A tough turf fight looms over which agency, and therefore which committee (Merchant Marine or Interior), should regulate ocean mining; on that question we pass.

There are a few other points still in contention. But most points represent a House consensus, one largely shared by the administration.

Indeed, by agreeing that legislation was appropriate, the administration got to help shape it. That meant removing from early drafts an unconscionable investment guarantee of up to $350 million per company if the loss was due to ratification of an unfavorable LOS treaty. The administration also lobbied successfully to have the law set up, from the companies' seabed proceeds, a fund for the international community-a bow to the concept that the seabed is the "common heritage" of mankind.

Some LOS buffs see a treaty principally as a vehicle and model of international cooperation. Believing that any nationally authorized seabed mining is harmful, they would put off all mining until the world agrees on how it should be done.

But that goes too far. Experts agree that existing international law governing the high seas assures American firms a right of access to the seabed. The House legislation would not confer sovereignty on American-mined sites. It would be superseded by a LOS treaty. It provides for revenue sharing with non-mining states. It sets up useful environmental and conservation controls.

The LOS talks, currently in recess, resume in New York on Aug. 21. The House will probably have acted by that time, and the Senate will be gearing up. Some harsh words will doubtless be said in New York about the Congress. But the international community should keep in mind that the legislation, while asserting an American interest, has been designed to preserve an international interest, too. It is, moreover, probably the minimal price that must be paid to ensure ratification of an eventual LOS treaty.