Despite Soviet reluctance to include regional conflicts on the summit agenda, President Reagan should actively pursue his United Nations pledge to seek negotiated settlements in Afghanistan and four other critical arenas of Soviet-American tension.

Afghanistan merits special emphasis because the danger of a superpower confrontation on the Afghan border is growing as Moscow steps up its threats of "hot pursuit" into Pakistan and as American weapons aid to the Afghan resistance escalates. Moreover, the three-year- old United Nations negotiations on the Afghan conflict are likely to collapse soon unless Moscow and Washington can break the deadlock on two key issues: the terms of a Soviet withdrawal and the future of the Soviet-sponsored Kabul regime.

The Soviet Union says that it is prepared to withdraw its combat forces from Afghanistan if the United States terminates its aid to the resistance under a procedural formula being negotiated by U.N. mediators. But the administration doubts that Moscow is actually ready for a complete force withdrawal within a defined time frame as envisaged in the U.N. scenario.

This American skepticism is fully justified by the hard-line position taken by the Soviet-sponsored Democratic Republic of Afghanistan in the August round of U.N. negotiations between the DRA and Pakistan. At the same time, Moscow believes that the United States has been quietly subverting the negotiations because the U.N. formula would legitimize the DRA regime.

The projected U.N. settlement would be in the form of three agreements, which would go into effect simultaneously: one between Pakistan and the DRA, barring aid to the resistance through Pakistani territory; another between Islamabad and Kabul, governing the return of the Afghan refugees now in Pakistan, and a third between Moscow and Kabul, defining the terms of the Soviet withdrawal. Identical declarations guaranteeing the settlement would also be issued by Moscow and Washington.

Detailed draft texts of the first two were agreed upon in August, but Moscow and Kabul refuse to negotiate their withdrawal agreement until Islamabad agrees to legitimize the Kabul regime by converting the present mediation process into direct talks. Islamabad, for its part, understandably wants to be sure that the Russians are prepared to make a time-frame commitment before it gives up its trump card. Pakistan has assured U.N. mediators that it will engage in direct talks if and when a settlement involving such a commitment is ready to be finalized.

The guarantee declaration was adopted at the June round and submitted to Moscow and Washington. Moscow responded with a revised draft in time for the August round, but Washington has remained mmittal. Against this background, the president's U.N. statement that "it might well be appropriate to consider guarantees for any agreements already reached" assumes potential significance.

The administration has not taken a clear position on the issue of direct talks. While nominally supportive of the U.N. effort, many officials argue that the DRA should be replaced as a precondition for a settlement, pointing to U.N. General Assembly resolutions that call for "self- determination for the Afghan people." By contrast, U.N. mediators believe that a Soviet withdrawal, per se, would satisfy the self-determination criterion and would force the Kabul regime to share power with noncommunist Afghans.

Under the U.N. scenario, the DRA would be left in place and would have a chance to survive, if it could, either through a political accommodation with its opponents or internecine military struggle, or both. The DRA argues that it could survive without a Soviet force presence if U.S. and other ad to the resistance were stopped. Administration officials ridicule this claim, but behind this diplomatic posture lies an unstated concern that the Kabul regime just might survive.

It should be remembered that the U.N. concept would permit the DRA to continue receiving Soviet economic and military aid while precluding further aid to the resistance. Intermittent fighting would no doubt continue between DRA forces and some resistance factions linked to pan-Islamic fundamentalist elements in the Persian Gulf and the Middle East. But the level of conflict in the countryside would be likely to subside, over time, as tribal and ethnic warlords make their uneasy peace with Kabul in return for local autonomy. The United States and other noncommunist countries should not prejudge whether the Russians could, or would, withdraw under this scenario but should focus instead on the quid pro quos that would make such a scenario acceptable.

The governing criterion for an acceptable settlement should be whether it prohibits Soviet bases. Apart from their ideological objections to legitimizing the Kabul regime, administration officials assume that the continuation of a communist regime would enable the Russians to maintain operational bases.

This argument has some validity, since the U.N. agreements deal only with Soviet combat forces and not with bases or advisers. But the president should use the summit to test Soviet interest in a trade-off based on U.S. readiness to guarantee the U.N. settlement in return for a Soviet withdrawal within a defined time frame, accompanied by satisfactory assurances foreclosing the use of military facilities in Afghanistan as Soviet bases.

The administration makes no pretense that the Russians are on the run in Afghanistan. As Pentagon intelligence specialist Elie D. Krakowski recently wrote, despite improvements in the combat effectiveness of the resistance, "the central factor is not absolute but relative performance, and in the latter, experts agree, the Soviets have widened the gap in their favor." Krakowski argues that more and better weaponry for the resistance will in time force Moscow to abandon the communist regime. But this roseate assessment ignores the depth of the historically rooted cleavages between resistance groups that make it so difficult for them to follow up their military victories by establishing secure liberated areas. Moreover, for every improvement in American-supplied weaponry, Moscow would be likely to counter with its own escalation, as it has done for the past five years.

More and better weaponry for the resistance is desirable, but not if its only serious purpose is to "make the Russians pay." The expansion of aid now taking place should be combined with a Realpolitik diplomacy designed to get Soviet forces and bases out of Afghanistan.