ISLAMABAD, PAKISTAN, NOV. 23 -- The approaching U.S.-Soviet summit in Washington has heightened a sense among western diplomats and Pakistani officials here that the eight-year-old war in Afghanistan may be entering what the diplomats call the "end game."

In this view, any discussion between Ronald Reagan and Mikhail Gorbachev of possible steps to end the war would add to other military and diplomatic moves that have been unfolding over the past year aimed at ending the conflict.

In the past several months, for example, the Soviet-backed government in Afghanistan is widely believed to have stepped up a campaign of terrorist bombings inside Pakistan in an effort to pressure the Pakistani government to soften its demands about how the war should be settled.

At the same time, Washington has stepped up pressure on Moscow and the Soviet-backed Afghan goverment by sending highly effective Stinger antiaircraft missiles to the Afghan resistance fighters; these weapons have reportedly taken a heavy toll on Soviet aircraft.

In addition, new Soviet statements about their reported desire to withdraw their forces have also contributed to the feeling that several components of a possible "end game" -- that rush of quick and decisive moves in chess that can bring the game rapidly to a conclusion -- may be at hand.

Whether the game is started in earnest, or the process postponed for another round of fighting, now depends on what the Soviet leadership tells U.S. officials in this week's talks in Geneva and at the summit, according to western and Pakistani diplomats who have closely monitored the progress of the Afghan war and the accompanying diplomatic maneuvering.

Some diplomats have long argued that the Afghan war, which has cost tens of thousands of lives and uprooted half that country's population, is likely to end only after Washington and Moscow reached an agreement that then could be implemented by the other parties in the conflict -- the Soviet-backed government in Kabul, the Afghan resistance and Pakistan.

Talk of the "end game" first surfaced a year ago when Soviet leader Mikhail Gorbachev and his aides began to suggest that Moscow was willing to reach an accord on withdrawing the estimated 120,000 Soviet troops in Afghanistan. It escalated when the U.N.-sponsored Geneva talks began to yield some progress on the details of that withdrawal.

When Undersecretary of State Michael Armacost met with Soviet Deputy Foreign Minister Yuli Vorontsov last week in Geneva to discuss regional issues expected to arise at the summit, the Soviet policymaker was "positive and forthcoming in reiterating the Soviet commitment to an early settlement," said one well-informed diplomat. "But it was mostly what the diplomats call 'body language.' We need more concrete ideas."

The "concrete ideas" refer not so much to the timetable for withdrawal of Soviet forces, but more to what will happen in Afghanistan when and after they leave. The Soviets fear a bloodbath that could decimate the communist regime that their troops supported for the past eight years.

"They just assume that once an agreement is reached, all of this will simply fall into place," said one well-informed diplomat, describing the thinking among the Afghan rebels and their U.S. and Pakistani supporters.

In this view, Moscow is the one that will have to take the initiative.

Pakistani and western diplomats here are warning that unless those "concrete ideas" are forthcoming, Moscow may find that the hand of hard-liners in the U.S. Senate who might oppose the summit's centerpiece -- the intermediate-range missile agreement -- could be strengthened when it comes to the ratification process.

Only a few months ago, when prospects of an arms accord seemed remote, diplomats familiar with the thinking in Washington were quick to deny any relationship between the subjects except in the overall context of U.S.-Soviet relations. Pakistani policymakers still question how far the United States is willing to go in using the arms agreement as a way to press home on Moscow the importance of settling the long-running Afghan war.

Because of Pakistan's proximity to the area of conflict in neighboring Afghanistan, the possibilities of a settlement are viewed with greater caution here than they appear to be seen in Washington.

According to diplomats and analysts in Islamabad, there are critical questions to be answered by all the major countries and forces involved in the Afghan war.

For the Soviet Union, there is the issue of whether Moscow will insist on the development of a communist-dominated regime before it pulls out its 120,000 troops. That issue is portrayed by western and Pakistani diplomats as the crucial one at the current phase.

Unless Moscow agrees to a genuine, broad-based government -- generally defined as one not including major figures of the current People's Democratic Party of Afghanistan -- the Peshawar-based Afghan resistance groups are likely to continue fighting.

For the United States and Pakistan, there is the question of what would happen if there is no agreement and the war continues. How long can each country sustain its current level of commitment?

For the Afghan rebels, there is the apparently unaddressed issue of what they will do if Moscow does make a serious settlement offer. So far, the guerrillas' fragile unified leadership is thinking in terms of setting a policy a year or 18 months from now.

For the current government in Kabul, there is the question of how and to what extent to press its Soviet backers for protection against retribution from more than 3 million Afghans who have fled the country.

Under the current formula worked out through extended U.N.-sponsored Pakistani-Afghan negotiations, the Soviet Union would agree to withdraw its troops under a certain timetable. Pakistan and the United States would agree to stop supporting the mujaheddin and seal the Pakistan-Afghan border. Afghan refugees would return to their homes.

Diplomats say that all parts of this equation are settled except the time frame of a Soviet pullout. Pakistan and the United States have been pressing for the pullout to be accomplished in less than a year, and the Soviets have been resisting until recently. Soviet Foreign Ministry spokesman Gennadi Gerasimov is reported to have referred to a seven- to 12-month formula in a recent interview, but he then quickly denied that he had used such language.

More recently, Moscow has shifted its focus to emphasize the necessity of an interim agreement to prevent massive bloodshed during and immediately after a Soviet troop withdrawal.

Officials familiar with U.S. thinking made it clear that if there is no settlement, they expect this winter's fighting to follow a different pattern from previous years. Instead of a winter respite, they expect the Afghan rebels to keep up pressure year-round.