For the third time in three years, United Nations Secretary-General Javier Perez de Cuellar is pushing for a settlement of the Afghanistan stalemate. His previous efforts had led to some movement, mostly procedural concessions by the parties involved. But recently the situation has remained frozen.
Mr. Perez de Cuellar has just sent Diego Cordovez, UN undersecretary-general for political affairs, on an exploratory expedition that will take him to Tehran , Kabul, and Islamabad.
This trip should enable Perez de Cuellar to determine whether a new round of talks in Geneva between Afghanistan and Pakistan, with the UN acting as an honest broker, should be launched later this spring.
To say there is little optimism at UN headquarters regarding Mr. Cordovez's mission is an understatement.
Perez de Cuellar feels that in order for a new round of Geneva talks to be meaningful, there must be some ''give'' by the parties involved on four issues:
* The Soviets (who are not now direct participants in the talks) must agree to a timetable for the withdrawal of their troops from Afghanistan in exchange for a Pakistani commitment not to interfere and intervene in the internal affairs of the country.
* The Soviets must give some indication regarding the nature of Afghanistan's future government if and when this country becomes nonaligned under the guarantee of the major powers and of its neighbors.
* The Soviets and the Afghanis must agree to the establishment of a mechanism to allow the Afghan refugees in Pakistan to return safely to their home and to be heard at the Geneva talks.
* Pakistan must show itself more willing to talk to Afghanistan officials directly.
''The Soviet Union might be willing, some day, to strike a deal with the US on a global scale, and in this context it might soften its position on Afghanistan,'' an informed Western diplomat says.
''But, given the sore state of Soviet-US relations at this time, the Soviets are not in a giving mood. Rather, they are eager to press their advantage wherever they can and to show that they cannot be pushed around. Thus Diego Cordovez could well come back empty-handed from his trip,'' he says.
US officials are privately skeptical about Cordovez's chances of making a breakthrough. Talks between Perez de Cuellar and Soviet and Pakistani officials in recent months have given the Secretary-General no reason to feel encouraged.
By personal inclination, Perez de Cuellar might have preferred not to pursue a diplomatic venture that many believe to be doomed to failure at least at this time.
But since Afghanistan and Pakistan both want the process to continue, the Secretary-General, as head of a peacekeeping organization, is not in a position to abandon his efforts.