The 35-nation conference on European security and cooperation opened here today with cautious East-West sparing and hopes that a showdown over human rights would be avoided.

The initial speeches at this highly publicized and potentially explosive meeting set a tough, yet restrained tone to the debate. The West appeared determined to push the conference into a thorough review of the human-rights situation in the East without reaching a confrontation. The East appeared prepared for an aggressive defense.

The Western argument was outlined by the Dutch delegate, Joop van der Valk, who told the opening session that his country was "disappointed" at how little "certain countries" had done to improve the human rights of their citizens.

"We cannot understand why repressive measures, even including imprisonment, are taken against those individuals who have commited no other crime than the exercise of their rights as recognized" under the 1975 Helsinki agreement that all 35-nations signed, he said.

Van Der Valk did not mention the names of any countries in his attack, however. In choosing not to do so, he helped set the tone for this meeting in which East and West will try and debate each other without causing a major blow-up.

Although the delegates here heard opening speeches by five countries today, it is the anticipation of what the Soviet and U.S. representatives will say on Thursday that is providing the tension concerning the future course of the entire conference.

Publicly and privately, delegates from both East and West are reporting a determined effort not to have a confrontation here over the emotional and controversial issue of human rights.

"It is simply very difficult to have a thorough review of how well the Helsinki accords have been implemented without having an element of confrontation built-in," said one U.S. official.

To get around an open confrontation, the speech by U.S. Ambassador Arthur Goldberg will deliver Thursday reportedly cites examples of shortcomings of human right in the Communist East, but it does not name specific countries. It also includes examples of American shortcomings.

The problem, however, is that chief Soviet delegate and the U.S. repre-address the hundres of delegates only about an hour before Goldberg speaks, and a harsh initial Soviet attack on the West would probably spark a prompt revision by Goldberg.

The personalities of both the chief Soviet delegate and the U.S. representatives are playing a part in the guessing game here about how the tone of the opening presentation by each will affect the future of the meeting. Experienced delegates say both men can become excited quickly over certain issues.

The appointment of Goldberg to head the U.S. delegation is likely to have prompted concern in Moscow, sources here believe.

"He is among the most famous civil liberatarians and most prominent Jews in the U.S." One delegates observed about the former Supreme Court justice and U.N. ambassador. "And he is very sensitive to the human-rights issue."

The first week of the conference is to be devoted to speeches made in public session by 33 European natons, the United States ad Canada - the signatory nations of the 1975 Helsinki agreements.

The following week, the session moves behind closed doors, first for a week of general debate among all countries and then for a series of special committees that will try and review progress, or lack of it, in living up to the 1975 agreements.

The conference here is slated to run at least until Dec. 22, although it could reconvene in mid-January for another month if necessary - a move the United States insisted upon as a means to avoid a Soviet filibuster on other subjects that might block discussion of human rights in a shorter conference.

The first glimpse of Communist commentaries on human rights came from the Romanian delegate who told the gathering that each country has its own values when it comes to human rights. He chided unnamed nations for encouraging emigration and luring specialized workers out of other countries.

Those actions, he said, are taken with aims other than the humanitarian purposes of the Helsinki accords, Romania has been under heavy pressure in recent years to allow both ethnic Germans and Jews to emigrate.

The delegates also heard a message today from Yugoslav President Tito, whose country is host to the conference.

Tito, the head of a Communist country but one outside the Soviet bloc, also spoke of Helsinki agreements that had been only hesitantly and inconsistently carried out.

Tito, however, as a leader of the so-called non-aligned nations, laid special emphasis on curbing the arms buildups on both sides which, he said, "not only increases mistrust but threatens to escape all human control."