As the United Nations heads for its 40th anniversary (next year) its leader ''keeps the faith.'' After 1,000 days in office, Peru's Javier Perez de Cuellar is widely considered to be the most effective UN Secretary-General since Sweden's Dag Hammarskjold.
He has managed to establish his personal credibility with all member states and has done much to improve the UN's image, if one can judge by the comments of scores of diplomats from Western, communist, and third-world nations.
After serving three years on the 38th floor of the international organization - and with two more years to go - he seems like Sisyphus of Greek mythology, who had been sentenced to roll a heavy rock every day up to the top of a mountain from where it always tumbled down.
''To keep doing this job one must heed Albert Camus' advice: Act as if you absolutely believe that justice, happiness, peace will prevail even when you are plagued with doubts in this regard,'' Mr. Perez de Cuellar said in an interview with the Monitor.
Yes, often, he says.
Discouraged? Never, he says. Patience, persistence, quiet diplomacy ''do work small miracles,'' he adds.
In some instances he feels that he has made progress in problem-solving and has ''accomplished something.''
The Secretary-General feels he has been effective in these areas in particular:
* Relations between the UN leadership and staff.
Relations have improved considerably in this area, he says. Perez De Cuellar says many problems remain to be solved. But morale, which was at its lowest three years ago, has improved because Perez de Cuellar has taken a personal interest in addressing the problems of individuals members of the UN staff.
* Control of UN expenses.
Ballooning expenditures have been brought under control and budget growth has been frozen.
* Earning trust.
Perez de Cuellar feels he has earned the trust of Israel, South Africa, Iran, and other nations that previously felt that they could not get a ''fair deal'' at the UN. ''There is now for the first time favorable talk in Israel about the UN's role in southern Lebanon,'' the Secretary-General says.
Many diplomats say that odd couples such as Afghanistan and Pakistan, Britain and Argentina, and Iraq and Iran feel that the Secretary-General is truly impartial and treats both sides with equal respect. ''The question of the UN's lack of partiality has ceased to exist,'' South Africa's Foreign Affairs Minister Roelof Botha said recently. Perez de Cuellar also established ''very good working relations with the Reagan administration.''
* Effective use of the UN's neutral ''good offices'' in areas of conflict.
The UN has provided Lebanese and Israeli military officers with a neutral shelter where they negotiate Israeli troop pullout from south Lebanon. Turkish and Greek Cypriots are inching toward an agreement through Perez de Cuellar's good offices. Iraq and Iran have allowed him to dispatch a mission to both countries in order to check on the use of poison gas. They have also agreed not to bomb civilian targets. And the Secretary-General has quietly kept pressing the superpowers to return to the arms talks and to keep up their efforts to resolve the Middle East conflict.
* Keeping a focus on human rights.
Perez de Cuellar has pushed hard, behind the scenes, on rights issues. Privately, he has intervened in many cases at the highest levels of leadership, including in the Soviet Union, Poland, Chile, and Ethiopia. As a result, individuals have been freed from jail or their lot has at least been improved.
* Hard work on the North-South dialogue.
He has tried hard to instill realism among third world and industrial countries involved in North-South economic talks. Perez de Cuellar has spared no effort over the past 18 months in calling the world's attention to the dramatic problems created by the drought in Africa.
But there are areas in which Secretary-General Perez de Cuellar feels much more needs to be done. The subjects that frustrate him most are:
* Arms control talks and economic negotiations.
For too long, the major powers have turned a deaf ear to his calls for negotiations, he says. Some countries still shrug when pressed on human rights. The ''haves'' and the ''have-nots'' (meaning rich and poor countries) are still ideologically and practically too rigid when discussing economic issues.
* Progress toward independence of several regions.
Negotiations regarding independence of Namibia (South-West Africa), Afghanistan, Kampuchea (Cambodia), and Cyprus still move at a snail's pace. The East-West polarization in recent years has frozen regional problems and limited the UN's room for manuever.
* Refusal to use the UN to settle disputes.
More often than not, member states refuse to use UN mechanisms for settling their disputes. The Security Council is often stymied by vetoes. This means that the Secretary-General must more and more often burden himself personally with the task of mediating between opposite sides.
''It is fashionable to criticize the UN. Yet it is at the UN that (President) Reagan, unveiled his plan last September for 'umbrella talks' with the Soviets on strategic issues and it is the General Assembly that gave (Soviet Foreign Minister Andrei) Gromyko an excuse to come to the US and meet with (US Secretary of State George) Shultz without losing face. In fact, while the administration has often been critical of the UN, this President has come to the UN and addressed the General Assembly three times in three years - a record for a US president,'' Perez de Cuellar says. ''The UN is here to stay and will not end up like the League of Nations, its predecessor, in the ashcan of history,'' the Secretary-General says. ''The powerful nations of the world will come to realize once more that they cannot manage all the world's problems and that the UN is very useful indeed as a face-saving device, a problem-solving mechanism, a forum where to conduct not only multilateral but also bilateral diplomacy, effectively and discreetly.''
Many heads of state are expected to come to New York for the UN's 40th anniversary next year.
''I don't want fireworks and festivities to mark the 40th General Assembly next fall.
''What I do expect, rather, is: (A) a serious recommitment by all member states to the UN Charter, (B) conceptual contributions from all sides with regard to what can be done to improve the UN system,'' he says.