Two prominent experts on Afghanistan said yesterday that the Soviet-backed government there is likely to fall with hardly a shot to Afghan resistance forces after Soviet troops withdraw from that country.

Both of the experts said they could not predict whether the takeover by members of the Afghan mujaheddin or "holy warriors" would take place immediately upon the Soviet withdrawal or after a short interval. But they said the resistance appears to be undertaking considerable discussion and even some planning about the takeover.

Thomas E. Gouttierre, director of the Center for Afghanistan Studies at the University of Nebraska, said leaders of the seven major Afghan resistance groups have discussed a joint operation to ring the capital city of Kabul after the Soviet defenders withdraw, and "my sense is, they've agreed on it."

Gouttierre said that by surrounding Kabul together and raising green flags of Islam, the resistance would bring about the hasty desertion of many of those associated with the Soviet-backed regime.

The former Peace Corps volunteer and academic expert, who heads the only U.S. scholarly center devoted exclusively to Afghanistan, said resistance leaders recently showed him passes allegedly issued by the Afghan Communist Party to its adherents to ease their travel to airports for evacuation to the Soviet Union.

The most effective way to avoid bloodshed and create stability, Gouttierre said, would be to create an interim regime without the current Afghan leader, Najibullah, or members of his Peoples Democratic Party of Afghanistan.

Gouttierre said the Soviet Union should encourage the creation of such a temporary regime to begin its postwar relations with the future Afghanistan on a stable and friendly basis.

Olivier Roy, a prominent French researcher who has made seven trips inside Afghanistan with resistance forces, sketched a similar scenario in remarks at Brookings Institution.

Roy said he believes that the southern Afghan cities of Kandahar and Herat will fall to the resistance within two days when the Soviet troops withdraw from there. The pullout probably will begin from the south to protect Soviet supply lines, he said.

The Soviets probably will give the Afghan resistance a detailed schedule of their troops' departure, and the mujaheddin will permit them to go peacefully and may even assign military police to assist the exit, Roy said.

Roy said he anticipates that Najibullah will be encouraged to resign for "health reasons" or otherwise ousted by the Soviets before their withdrawal from Kabul and replaced with a temporary regime, possibly led by a military figure, which might be more acceptable to the resistance.

If the Soviet-backed government was unable to govern effectively with 115,000 Soviet troops in the country, "it's absolutely impossible for it to do so with no Soviet soldiers," said Roy, whose lecture was attended by several officials of the National Security Council, State Department and Defense Department.

If the resistance groups remain united, said Roy, there will be "a decisive psychological moment" after the Soviet troops withdraw "when people will say, 'It's finished' and suddenly they'll go to the other side."