Sea law treaty goes ahead - with or without the US

The Law of the Sea treaty will become customary international maritime law once it is ratified by at least 60 nations - even though the United States voted against it.

The treaty was adopted by an overwhelming majority April 30. One hundred and thirty nations voted in favor of it, four against (the US, Venezuela, Israel, and Turkey), and 17 abstained (among them West Germany, Britain,the USSR). France and Japan resisted last minute high-level US pressures and voted in favor of the treaty.

Many diplomats here expect that a future US administration will eventually sign the treaty. And they add that West Germany, Britain, and Italy - all of which abstained under heavy US pressure and in order not to allow the US to be isolated - also will probably sign the treaty later on. So, too, will the Soviet Union, say these diplomats, despite Moscow's concern that its state mining operation may face a disadvantage under the treaty.

According to the head of the US delegation, James Malone, ''the United States has not at this time decided whether to sign the treaty or not.'' And a Western diplomat comments that ''the door is open for another administration, less rigidly opposed to anything 'multilateral' to return to the fold of the world community and sign the treaty.''

US enterprises, which will have the necessary technology by 1990 to mine the deep sea beds, will have to operate under the treaty's umbrella. Otherwise, say experts here, they will not be covered by insurance companies since any US enterprise which mined unilaterally could be held to have acted illegally by the International Court of Justice at the Hague.

Ninety-eight percent of the treaty's provisions were reached by consensus, with US participation. The US, for instance, has been guaranteed a seat on the Council of the Sea Bed Authority. Washington's concern that it could be outvoted by the developing nations in 20 years time at the proposed revision-of-the-treaty conference was dealt with by making any such revisions subject to concensus, thereby in effect giving the US a veto.

But despite efforts to satisfy US demands, the US shocked some of its best friends in the West and in the third world by refusing to let the final treaty pass by concensus, and instead forced the last minute roll call vote.