An unexpected and unsolicited State Department statement on Jan. 26 was the beginning - an announcement that the new United States government was concerned about the fate of intellectuals in Czechoslovakia who had petitioned their government for more freedom.

The Nixon and Ford administrations never volunteered such statements, so this was a surprise, at least in some diplomatic circles. It was also the first trickle in what soon grew into a verbal flood.

The new American government quickly made a succession of unprecedented statements supporting dissidents in the Soviet bloc, culminating in the startling revelation that the President had written a warm personal letter to the leading dissident intellectual in the Soviet Union, Andrei Sakharov.

The "human rights" issue became one of the major stories of Carter's first month although - from the very first statement on the Czechoslovakia petitioners - the new administration was improvising. President Carter was acting on strong personal beliefs and political commitments, but the precise measure he and his associates took were carefully planned only once - when they decided to send the letter to Sakharov in Moscow (a move the State Department said might not be appropriate).

"The whole thing has grown like Topsy and seems to be feeding on itself," one State Department official observed. In a series of interviews last week, numerous officials involved in these events acknowledged that the Carter administration still does not have a comprehensive and consistent policy on human rights. Some doubted one could be developed, given the uncertainty of future events.

Nevertheless, the young administration has managed in a month to radically alter the tone of the Soviet-American relationship - so radically, in the view of some diplomats, that future negotiations on political and arms issues may be adversely affected.

This is the message that the Soviet ambassador, Anatoliy F. Dobrynin, has tried - forcefully if indirectly - to deliver in recent weeks. According to reliable sources, Dobrynin has told the new administration repeatedly that Chairman Leonid I. Brezhnev personally insists that non-intervention in Soviet affairs be a basic element of the still-evolving Soviet-American relationship.

Administration officials say the new U.S. posture - though it involves basic principles - should not influence negotiations in other fields. During the same period that the human rights issue has been blossoming, President Carter has repeatedly invited the Russians to begin serious new arms negotiations.

Carter began to take advantage of the Ford-Kissinger approach to decents early last year.

Ford's refusal to invite Alexander Solzhenitsyn to the White House, and his efforts to hobble the congressionally mandated commission that was supposed to monitor the human rights provisions of the Helsinki agreement on European security, made useful campaign issues for the Georgian, particularly in ethnic communities of East Europeans.

This all came to a head in the second campaign debate, when Ford made his famous slip: "There is no Soviet domination of Eastern Europe and there never will be under a Ford administration." Carter picked this up with gusto: it soon became the biggest issue" of the campaign. Carter emerged from the episode as the outspoken champion of those dominated by Soviet power.

The Carter administration has been surprised - some of its officials alarmed - by the amount of publicity the new human rights posture has generated already, and to some extent their surprise seems justified. The new President and his associates did signal their intentions on this issue more than once prior to Jan. 20.

During the campaign, for example, Carter wrote an encouraging letter to Vladimir Slepak, a leading Jewish dissident in Moscow. In December, Cyrus Vance, then Secretary of State-designate, met in New York with Andrei Amalrik, a leading Soviet dissident who was pressured to leave the Soviet Union last year.

Both these gestures departed from the posture that Secretary of State Henry A. Kissinger had urged on Nixon and Ford, and - coupled with Carter's outspoken campaign rhetoric on human rights - they were probably signals of what was to come. But diplomats, particularly, tend to discount campaign rhetoric and behavior; many weren't prepared for Carter the President to act like Carter the candidate.

The new administration position was first enunciated almost by chance. Just a few days after the inauguration, Vance had dinner with several reporters who regularly cover the State Department. One of them suggested that Vance might change a frustrating department habit.

The habit was to prepare statements on world events to use in case a reporter asked for a comment at the department's daily news briefing. If no one asked the right question, the statement was never made.

The reporter asked if the press offices could simply release these statements when the department had gone to the trouble of preparing them. The new secretary thought it was a reasonable idea.

The very next day, without being asked, Frederick Z. Brown, the department spokesman, announced at the noon briefing that the U.S. government was concerned about mistreatmentof Czechoslovak intellectuals who had signed a petition asking their government to grant more individual liberty. The reporters were surprised. One of them asked if the department also had something to say against Sakharov, who had been summoned to the prosecutor's office in Moscow a day earlier and given a stern warning. No, Brown said, but he'd inquire.

The next day the department issued a statement in defense of Sakharov, observing: "Any attempts by the Soviet authorities to intimidate Mr. Sakharov will not silence legitimate criticism in the Soviet Union . . ."

This was front-page news. It was also a surprise to the President and his Secretary of State. Vance had personally cleared the statement on Czechoslovakia, but this one was released after clearance by a deputy assistant secretary of state. "A glitch in our system,' a senior official later explained. But Vance and Carter stood by the statement.

On Feb. 2 Carter had his first meeting with Dobrynin. According to well-placed sources, the President went beyond the advice of his aides to tell Dobrynin explicitly of U.S. interest in human rights. He also offered several new ideas for the strategic arms limitation talks (SALT), attempting to demonstrate the new administration's determination to negotiate a new SALT treaty quickly.

At that very moment the bureaucracy was analyzing a personal letter that Carter had received from Sakharov. It had been brought to the White House by a New York lawyer, Martin Garbus, whohad met Sakharov on a tourist trip to Moscow. (Garbus originally planned to release the letter to the press; an acquaintance suggested he ought to give it to the addressee, Carter.)

The State Department drafted a possible reply for Carter, which it forwarded to the White House with an accompanying analysis. That analysis noted that Sakharov did not seem to solicit or expect a personal reply from the President. However, he did ask - in a paragraph of the letter previously unpublicized - for a channel through which he might convey important information on human rights matters to the United States. The State Department suggested than an appropriate reply might be for a low-level American official in Moscow to meet Sakhrov there.

Carter rejected this advice. In the end he wrote his letter to Sakharov himself. It was sent - through the diplomatic pouch to the embassy in Moscow - on Feb. 5.

This letter was, in effect, in the mail while the American news media, various Western governments and specialists on Soviet affairs conducted an unstructed debate on the merits of the new American posture. Replies by Vance and Carter to public questions were interpreted by some as steps back from the earlier statements on human rights. But that analysis went up in smoke when Sakharov - on Feb. 17 - revealed to the world that he had received his letter from the President.

That same night Dobrynin went to the State Department for a heated meeting with the acting secretary of state (Vance was in the Middle East). Dobrynin angrily cited the original Soviet-American correspondence of 1933, in which both governments pledged not to interfere in each other's internal affairs in any way.

A few days earlier, the Soviets' official organ, Pravda, had warned the world against interference in internal affairs. Since Dobrynin's firm demarche of Feb. 17 there has been a steady stream of similar complaints and warnings. The latest appeared in Pravda yesterday.

What does this all add up to? Thus far, a confused picture. The Carter Administration has certainly established a new posture and a new way of handling this issue. Last week the United State extended its new position to countries outside the Soviet bloc with an announcement that military aid would be cut to Argentina, Ethiopia and Uruguay because their governments were abusing human rights.

Administration officials argue that Carter had to speak out firmly on Soviet repression to help revive domestic support for detente generally. Progress on arms control, Carter was said to feel, depends on a reliable consensus at home - which Ford and Kissinger squandered during 1976.

Prof. Jerry Hough of Duke University, a Soviet specialist, argued in an interview that Carter risked raising false hopes with his new posture. "In the case of particular individuals," Hough said, "the new policy may have an impact . . . but in terms of promoting liberalization in the Soviet Union it will do no good . . . What happens when it doesn't produce anything productive?"

A senator State Department official noted that after the Carter administration made a public statement depolring the arrest of Alexander Ginzburg, a Soviet dissident, another dissident who had been hiding from the secret police emerged to say this statement helped protect him. Soon afterward the second dissident, Yuri Orlov, was arrested by the KGB.

Proponents of the new posture respond that the United States has put the Soviets on the defensive, confused them, and also made them realize that Carter is serious about human rights. All those are positive, in terms of both domestic politics and relations with the Soviets, some officials argue.

The Soviet regime did make "strong welcoming noises" to the Carter administration, as one government official put it. Brezhnev himself, in a speech just before the inauguration, seemed to promise a cooperative attitude. Now Carter has surprised the Russians on a new front.