MAYBE PRESIDENT CARTER was trying to do too much in his Annapolis speech yesterday. He was trying to resolve disputes within his own government, to reassure the public of his firmness toward the Soviets and his mastery of foreign policy and - above all - to give the Russians a clear sense of what this country requires of detente. It was not a great speech. But it was a useful speech if only because some comprehensive statement of presidential policy was urgently needed. For several weeks now we have seen the air positively clogged with policy bits and pieces and preferences launched both openly and anonymously by Carter subordinates - a policy equivalent of orbiting space junk.

It can be argued that the president merely gathered all the bits and pieces into one speech and prclaimed the results to be his policy. Certainly there were identifiable traces of Zbigniew Brzezinski's conceptual view of great-power relationships and Secretary of State Cyrus Vance's tactical approach, and that lent the speech a certain on-the-one-hand-on-the-other quality. But the point is that there is now a document on the record embodying Jimmy Carter's policy on the most fundamental questions of the U.S.-Soviet relationship. And while that in itself is no guarantee that the infighting will cease (it won't), there is an important message here that takes precedence over the contradictory signals and assertions of lesser officials.

The president told the Russians he had noticed what they were doing lately - and that he didn't like it. They couldn't have detente both ways, he said: "The Soviet Union can choose either confrontation or cooperation. The United States is adequately prepared to meet either choice." Some of his formulations struck us as rather strange. He cited Korea, Angola and Ethiopia an evidence of the Russians' penchant for using "proxy forces" to achieve their purposes. The catalogue seems strangely mismatched and incomplete. Korea and Angola and separated not only by an enormous difference in the kinds of operations involved but also by a 20-year interval in which the Soviets, among other things, sent missiles into Cuba and essential military aid into North Vietnam, to cite but two curious omissions. And some of his characterizations of the Soviet system were gratuitously provocative, or scratchy anyway. But Mr. Carter did, in the core if his speech, manage to enunciate the elements of the bargain he would strike.

He promised to negotiate "constructively and persistently for a strategic arms limitation agreement." And he said he had no desire to link the arms talks to the rest of the U.S.-Soviet relationship. But he took pains to point out that there is such a link, in practical politic terms: "In a democratic society . . . we recognize that tensions, sharp disputes or threats to peace will complicate the quest for an agreement." And he alluded to at least some areas of tension where Soviet forbearance would be a test: Rhodesia, Namibia, Eritrea and Angola. The president put it squarely: "A competition without restraint and without shared rules will escalate into graver tensions, and our relationship as a whole will suffer. "He hinted that at a minimum the casualities of continued Soviet intransigence or expansionism would be "improved trade and technological and cultural exchange."

There is one fundamental condition on which the value of the president's speech rests. It is that he impose and continue to impose on his government the discipline that the mere preparation of such a speech implies. The president, in other words, has enunciated a government approach toward the Soviet Union. In so doing, he has at least defined the outlines of a coherent policy. To keep it coherent will require almost the daily exercise of his authority.