The 35 nation conference to review the Helsinki accords on European security, which at one point looked like it might become a monumental clash between East and West over human rights, is now shaping up as a more gentlemanly affair aimed at preserving whatever is left of detente.

"Things are definitely more relaxed now. There is much less tension," said a senior Western European diplomat on the eve of the reconvening of the conference Tuesday in the Yugoslav capital.

A top American delegate here said, "There will be no confrontation at the conference . . . I don't even like to use that word . . . therefore, there will be no jeapordizing of crucial issues."

Delegates from 33 Eastern and Western European nations plus the United States and Canada are gathering here to review progress, or lack of it, made by their governments in implementing the Helsinki agreements that they all signed in August, 1975.

Although those accords dealt with many economic and security questions, they also pledged all signers to respect "human rights . . . fundamental freedoms . . . and the free movement" of people and ideas.

It was that provision, more than anything else, that captured the attention of large numbers of dissidents in Eastern Europe and a new American President who termed his commitment to human rights as "absolute."

A seven-week preparatory conference aimed at setting up the agenda for the main review meeting was completed here early in August.

Although the participants eventually agreed on an agenda, their lengthy struggle behind closed doors illustrated how hard it will be to score debating points publicly in the Belgrade forum and to achieve anything controversial in a conference that requires consensus.

Behind the Western views that the conference is now less apt to erupt into a confrontation the rather widespread feeling that the Carter administration has toned down its previously outspoken campaign on behalf of human-rights activities, especially those in the Soviet Union, in favor of a quieter and more generalized approach.

Several factors are cited by Western diplomats, including the political maturation of the new administration and an unwillingness by the United States to totally paralyze its foreign policy by continuing to hammer at the Soviets on an issue that angers and embarrassed them.

Others cite the acceptance of more cautious Western European views on dealing with the Soviets.

Most importantly, however, is the feeling that the United States does not want to jeopardize new signs of progress on the crucial nuclear arms limitation talks by forcing a confrontation here in the coming weeks over human rights.

What the new Western strategy going into the Belgrade conference amounts to, another diplomat says, is "a blending of views that have done both the Carter administration and its West European allies good."

Thus, he says, the human-rights issue will be pressed "in categories rather than cases. Rather than press specific individual problems, one Westerners says. "We would like to know why a Soviet who wants to emigrate must pay six months wages for a passport or why an East German who asks to go to West Germany is apt to lose his job."

The new U.S. ambassador to the talks, Arthur Goldberg, has said the United States would express its concerns "in all areas covered by the Helsinki final act, including that of human rights, in a clear and forthright manner" the phrase that is ringing in Western European ears, however, is Goldberg's statement that "we seek no confrontation."

"Things still could get out of hand and the human-rights card is still an important trump, but we've really dropped the big stick for the time being," one American said.

The West is also expected to focus more attention on economic issues, an area in which the Soviets are intensely interested. "The more you do business with the Russians, the more you must realize that you've got to have relations in all areas in a businesslike manner," one official said.

Westerners insist that the NATO allies have a united position on key issues going into the conference. Goldberg reportedly told the delegates from the NATO countries at a Brussels meeting Sept. 28 that cohesion within the alliance was the top priority.

The only issue that might split allied unity is human rights and the general view is that if the Americans do not press to hard, no one else will.

Eastern bloc countries in the months since preparations began in earnest for the Belgrade review, have done their best to get ride of citizens who might demand greater attention to civil rights.

East Germany has exiled a score of prominent cultural figures to the West in recent months and has ransomed hundreds of other "political prisoners" to West Germany. Czechoslovakia has also forced some of its more well-known dissidents to leave and has jailed or isolated many others. The Soviet Union has managed to either isolate, arrest or exile virtually all of the most vocal dissidents and monitors of the Helsinki accords.