A day spent looking into the United Nations' three- year effort to negotiate a settlement in Afghanistan is a sobering day.

There is the abstractness of it all. In effect, the U.N. has a checkbook but not a bank account. In the Afghan negotiation, it has actually written three "checks" -- draft agreements to exclude Pakistani support of the insurgents, to let the Afghan refugees return home and to have the two great powers guarantee a deal, as the United States has now said it will.

The one "check" that remains to be written is a Soviet withdrawal timetable. Then it will be necessary only to figure out whether to do all this consecutively or simultaneously -- a standard diplomatic exercise. But there is no visible prospect of a payout on any of these "checks."

Why not? You have to ask what is going on in this negotiation. The optimists at the U.N. see it as building a framework that could become real if the parties and their patrons would but make it real. So it is that Secretary General Javier Perez de Cuellar identifies the current holdup as "a question of political will." It is both the glory and the undoing of the U.N. that it hesitates to acknowledge there are true conflicts of national interest. It hopes problems can be reduced by the solvent of "political will."

The pessimists, who include here the American government, find deep conflicts of national interest. They tend to see the Afghan negotiation as an exercise in which the secretary general and his man for Afghanistan, Diego Cordovez, are making gestures, weaving paper webs.

The Americans, furthermore, think the U.N. team is a bit too ready to let the Russians use the negotiation to distract attention from their atrocities in Afghanistan. The Americans would probably be more upset if the Russians were not already plainly tagged as the heavies, or if they thought the negotiations were going anywhere.

It rankles them that the U.N. encouraged the Afghan bid last August to change the indirect Afghan-Pakistan talks into direct talks. The Pakistanis refused on grounds that they were being asked to make an uncompensated play of the ace -- their recognition of the Kabul regime -- that they mean to save for a Soviet withdrawal timetable.

In any event, there is an evident near-total distrust between the parties and their patrons. The Russians say they feel that deep down Ronald Reagan wants only to bleed them and humiliate them. The Americans say the Russians are not hurting enough yet and that anyway, the Russians, having made such an immense six-year investment, will not accept anything less now than permanent control. Each may be making the other right.

At the Geneva summit, Mikhail Gorbachev offered a brief formulation of the Afghan problem that his listeners found not so much promising as interestingly ambiguous. Without giving anything away, he seemed realistic about the heavy costs of the war to Moscow and open to the idea of a political solution. Washington, acting on its premise that a solution depends first on a Soviet rethinking, decided to publicize the new Soviet wisps in order to smoke Moscow out. It's keeping a close eye on the round of Afghan-Pakistan talks the U.N. opens in Geneva next week. Under the surface of the U.N. negotiation, meanwhile, flickers the idea of an eventual face-saving solution: at some point Moscow must abandon quisling Babrak Karmal and -- here is a formidable project -- find an Afghan leader acceptable both to it and to Pakistani President Zia ul-Haq, who needs a man in Kabul whom he can impose upon the resistance that he supports out of Peshawar.

For this to happen, many people need to do many things. Certainly the priority is for the Soviets to stop slaughtering the population. The United States has its own considerations:

Jimmy Carter asked the Kremlin not just to pull out its troops but to turn back the political clock in Kabul, and to turn back the clock not just to before the Soviet intervention of December 1979 but to before the coup of April 1978 that brought a communist regime to power -- a coup the United States had been living with. This is an exceedingly ambitious goal, and it puts a heavy burden on negotiations. President Reagan's vigorous military and political support of the Afghan insurgents may add to it.

Then, we have got to match our Afghan policy better to Afghan politics. I am no student of the latter and do not feel confident to pick among the experts. Increasingly, however, I have the queasy feeling that the United States rather casually let Pakistan pick its Afghan friends for it and as a result we are backing the fundamentalist never-compromisers and not the tribal maybe- compromisers among the mu A fresh eye might turn up some new possibilities. Admiral Poindexter?