There are signs of a prospective rift between the United States and Pakistan on the terms on which a settlement of the Afghan crisis might be negotiated. Since the negotiation is moving forward, this could become a more serious matter soon.

First word of the gap came in an article in The New York Times last Monday by Selig S. Harrison, a veteran South Asia hand. He suggested that Pakistan has been getting ready to negotiate a regional settlement but that the United States is holding out for a broader Soviet-American bargain and, in Afghanistan, for more rigid terms than Moscow is likely to accept. Specifically, Pakistan appears to accept, and the United States to reject, the key Soviet condition that the Soviet regime in Kabul remain in place at the outset of a settlement process.

Pakistan's President Mohammed Zia ul-Haq was in Washington this week, and I asked him about his meeting with the new Soviet leader, Yuri Andropov, at the Brezhnev funeral last month. Zia said they had spent almost all 50 minutes talking about Afghanistan. Andropov, he said, was "fairly well impressed" with what the world thinks about the Soviet role in Afghanistan and wants to "pacify public opinion." He advised Andropov, Zia said, to cooperate with the indirect negotiations the United Nations has been conducting, with the Afghans, Pakistanis and Iranians, and his advice had "gone home."

Would Pakistan accept the Soviet condition that the Babrak Karmal government remain in place at the outset--as Soviet troops withdraw, as the borders are sealed and as the refugees return?

"Negative," declared Zia, a military man, adding that the whole Pakistani purpose was to avoid endorsing the Afghan figure installed by Soviet tanks.

Subsequently it was possible to take other soundings, and now it seems to me that Zia's resounding "negative" requires a closer look. His answer referred specifically to Karmal. If he were replaced by Moscow before or during the unfolding of a settlement, the makings of a deal might be there.

If so, the administration will face a question it does not appear to have closed with so far: whether to take its lead from Pakistan, which may have its own reasons to seek accommodation, or use American influence against the sort of agreement that did not fully serve the American idea of what a settlement ought to be.

A moment of truth, or half-truth, may come as soon as January. The U.N.'s negotiator, Undersecretary General Diego Cordovez, will then carry out to the area some sharp questions, requiring specific answers, based on the package of understandings he discussed with the Pakistanis and Afghans last July. There are those who feel the vibrations of imminent movement in the air.

For Moscow, the direct costs of continued intervention are substantial: casualties, treasure, diplomatic losses on all circuits. As a new man, Andropov, conceivably has some room to call it "Brezhnev's war" and cut Soviet losses. The Chinese have listed an Afghanistan settlement as a priority in the mutual improvement of relations being pursued now by both Moscow and Peking.

Washington is of a mind and at enough of a distance to define the war as one of principle. "The Afghan people are fighting for their own survival, but their struggle has a much broader meaning," Ambassador Jeane J. Kirkpatrick says.

Certainly the Pakistanis, least of all the stern Gen. Zia, do not need to have the principle spelled out. But they, and even Zia, realize they bear a heavy burden, and they can sometimes be heard quietly wondering whether the American purpose is to get the Soviets out of Afghanistan or to watch the Soviets bleed there. The Pakistanis, not seeing themselves as players in a global contest, want only to regain a non-threatening neighbor.

The Americans fear the U.N. negotiation may end up endorsing Soviet puppet rule or ensconcing Soviet forward bases. At the same time, they are sensitive to any suggestion that their interests differ from the Pakistanis'. Washington provides the aid and encouragement, Islamabad takes the risks: there is an imbalance. On the American side at least, the potential for misunderstanding seems not to have been recognized.