THE CARTER ADMINISTRATIONS talks with the Soviet Union on the Indian Ocean seem to have struck an embarassing snag. The President, you will recall, early on sought negotiations to "completely demilitarize" that sprawling region. It was not clear, however, that he had been fully briefed on the military activities the United States conducts there: a $100-million base is being built on the island of Diego Garcia, carrier task forces and missile-carrying submarines move in from time to time and arrangements exist with various states to patrol the sea lanes through which America-bound oil passes. By contrast, the Russians sail small surface ships around where they can. Only, it appears, when this discrepancy in usage was recognized at the White House were our negotiating goals reduced from "complete demilitarization" to "mutual restraint."

The Russians, however, have tossed in a little monkey wrench. They recently lost their major littoral foothold, in Somalia. Since being thrown out, it is reported, they have decided that it's not enough to stabilize the situation; what's needed is to reduce the big-power military presence and, specifically, to exclude nuclear-powered vessels. Such restrictions wouldn't bear considerably more heavily on the United States, which conducts most of the significant military activity in the region. So it is that some officials are nor said to feel no agreement is that some officials are how said to feel no agreement is possible unless the Soviet fleet once again achieves a secure foothold in the Indian Ocean. In other words, the negotiation can't move forward until Moscow increases its naval presence - a curious position for a negiotation aimed at limitations to be in.

Well, it's early in the Indian Ocean talks, too early no doubt, to conclude that this snag can't be overcome. The subject is a new one in big-power dialogue; there is much to learn. Navies may love naval competition, but the two governments would appear to share an interest in minimizing it, in seeing that the existing competition does not provoke excessive political tensions, and in heading off an unnecessary naval arms race.

If naval competition in the Indian Ocean is rally all that serious, however, then the United States may have reason to consider what steps it could take on its own. The Diego Garcia base, for instance, was undertaken on grounds that the Russians already had a base at Berbera in Somalia. Now Berbera is wiped out, but work proceeds apace at Diego Garcia. It would be ironic - and indefensible - if negiotations were to become a cover for the further one-sided militarization of the Indian Ocean.