TOMORROW's signing in Geneva of a pact between Afghanistan and Pakistan caps six long years of United Nations negotiations; it marks a major step forward for the forces of human freedom. After more than eight years of fighting Afghan guerrillas who have bravely refused to submit to foreign occupation, the Soviet Union at last sees the merits of a graceful exit. In its first voluntary retreat from any attempt at territorial domination since leaving Austria in 1955, Moscow has pledged to pull its 115,000 troops out of Afghanistan within nine months.
Yet the agreement is no peace accord in the usual sense. It calls for no cease-fire. Fighting between the current alliance of seven Afghan resistance groups and the communist Afghan government forces is likely to go on.
Under a new side agreement to the treaty, Washington and Moscow have agreed to ``positive symmetry'' in supplying aid respectively to the resistance fighters and the Afghan government. As long as the Soviets continue sending aid to their ally, so may the United States.
Under an earlier plan the US would have ended its aid to Afghan guerrillas in exchange for the Soviet troop withdrawal; strong pressure from Congress forced the US to increase its demand. Massive stockpiling of arms has occurred on both sides of the Afghanistan war in recent months; supplies could last a year.
How well the new agreement succeeds and whether or not the 5 million Afghan refugees in Pakistan and Iran return home depend largely on what kind of government takes shape in Kabul.
Mohammad Najibullah, the present Afghan ruler, has been urging all forces of the opposition to join him in a government of national reconciliation. Muslim guerrillas, who view the new pact as a sellout, want no part of any communist coalition; they vow to fight until the last Soviet soldier is out and an Islamic government is installed in Kabul.
On their behalf and with its own 3 million refugee load in mind, Pakistan at one point demanded that Najibullah be replaced with a transition government dominated by guerrillas and headed by an Islamic fundamentalist. Getting nowhere, Pakistan finally dropped the demand.
The task now is to reach some kind of compromise on an interim government. The US has been preoccupied with the Soviet troop issue, and a number of US officials have assumed that the resistance can and, in time, will, overthrow the Kabul government by military force.
The US and Soviet Union, who will initial the new treaty as guarantors, should take that role seriously and exert positive pressure to resolve the cause of the fighting. The superpowers can make a vital difference in the shape of the next government; they must decide whether to continue underwriting civil war or to put their weight behind negotiations.
The effort will test the ability of moderate political groups as well as of extreme Islamic fundamentalists to set aside their differences and compromise in the national interest. If no interim government evolves, the agreement could well break down in a year or so; the accord basically buys the Afghans some time.
Getting the Soviet troops out of Afghanistan is a major achievement that should lead to at least some reduction in fighting. Resistance forces may insist nothing has changed, but they have largely been fighting Russian troops. The superpowers should now pave the way for a more lasting peace accord by supporting the efforts to form a moderate transitional government.