U.S. and Soviets Will Halt Afghan Arms Aid by Jan. 1 : Diplomacy: The accord opens the way for negotiations to end the 13-year civil war. It resolves another major Washington-Moscow dispute.

The Soviet Union and the United States agreed Friday to halt all military aid to the warring factions in Afghanistan as of Jan. 1, opening the way for a negotiated end to a 13-year civil war that has killed hundreds of thousands of people.

The two superpowers had poured billions of dollars of military equipment into Afghanistan--the Soviets openly supporting a Communist government, the United States covertly backing Muslim rebels--since the Soviet army invaded the country in late 1979 to prop up a regime that had been battling insurgents for more than a year. The Soviet troops withdrew in 1988-89.

Secretary of State James A. Baker III, who announced the deal jointly with Soviet Foreign Minister Boris D. Pankin, said it represents the resolution of a third major U.S.-Soviet dispute in the three weeks since the collapse of a hard-line coup against Soviet President Mikhail S. Gorbachev. The Soviet Union in recent days also has decided to begin pulling its troops out of Cuba and to recognize the independence of its three Baltic republics, Lithuania, Latvia and Estonia.

“This removes, it seems to me, three of the most contentious . . . items that have impeded and obstructed progress in (the U.S.-Soviet) relationship,” Baker said.

Officials acknowledged that the new Afghan accord, which calls on the United Nations to oversee “a credible electoral process . . . leading to the establishment of a new government that will have the broad support of the Afghan people,” is unlikely by itself to stop the fighting.

In a sense, they conceded, the superpowers are washing their hands of their former clients’ quarrel and dumping the problem into the lap of the United Nations.

The United States and the Soviet Union had been working toward an Afghan settlement, including a cutoff of military aid, since early 1990. But until now, U.S. officials said, hard-liners in the Soviet military had resisted a deal.

The quick agreement on the terms of the deal reflected the eclipse of the military’s influence in Moscow after the failure of the hard-liners’ coup attempt last month, U.S. officials said.

The accord dealt a heavy blow to President Najibullah, the leader of Afghanistan’s Communist regime. He relied heavily on Soviet-supplied armaments to fend off rebels.

Najibullah summoned his Cabinet and party leaders to an emergency meeting in Kabul to discuss the impact of the accord.

“It will certainly put Najibullah and his regime under pressure,” said one Asian military analyst in the Afghan capital.

Baker and Pankin appeared to agree that Najibullah could remain in place as the titular chief of government, as long as much of his regime’s power is transferred to an interim U.N.-sanctioned authority during the run-up to elections. The Afghan rebels have long demanded that Najibullah step down before any elections could be held.

“We expect that all the (warring) parties and the Najibullah government will contribute to that process” of arranging an interim authority, Pankin said. “After that, elections will be held in the country, and the outcome of those elections will see who will stay in power and who will go.”

The main aim of the interim authority, Baker said, is to ensure that the Najibullah regime does “not have the ability or influence to skew the elections. The details of that mechanism, how it’s going to work and what elements of the government will be supervised by (or) transferred to the U.N. authority, all of those details really still have to be worked out.”

Both Baker and Pankin said they expect the aid cutoff to force the two sides to negotiate seriously with each other for the first time.

Yevgeny M. Primakov, Gorbachev’s foreign policy adviser, is now in the Mideast, talking with leaders in Saudi Arabia and Iran, two of the Afghan rebels’ principal backers, to promote the dialogue.

“We are working to get the message through to both sides that the time for peace has come and that we and the Americans will do everything we can to end this war,” Vitaly I. Churkin, the Soviet Foreign Ministry’s spokesman, said. “And we . . . will be seeking direct discussions with the Afghan opposition. We think that would help accelerate the search for peace.”

Acknowledging that Soviet policy has shifted in the wake of the abortive coup against Gorbachev, Churkin said: “We have been trying for some time to de-ideologize our foreign policy. The events in August . . . have allowed us to take several steps in this direction, and not only in our relations with the United States.”

The United States and the Soviet Union agreed to refrain from increasing aid before the Jan. 1 cutoff and to encourage other countries to halt their military aid as well.

They also decided to withdraw their “major weapons systems” from Afghanistan. This could include Soviet missiles and bombers and U.S. Stinger antiaircraft missiles.

Finally, the two sides promised to mount a joint program of humanitarian aid to impoverished Afghanistan.

American officials said the United States and the Soviet Union had been close to an agreement on these same terms in August and again in December, 1990. Each time, they said, Soviet conservatives blocked the accord.

The negotiations gained new impetus, in the U.S. view, after the coup eliminated the hard-liners and after U.S. experts warned that the civil war could erupt anew as food shortages in Afghanistan worsen this winter.

But Soviet officials suggested that the U.S. position had shifted more than theirs.

Some U.S. officials forecast the possibility of fighting not only between the government and the guerrillas, but among different factions of the guerrillas themselves--a prospect that pushed both Washington and Moscow toward agreement.

Over the last decade, beginning under President Jimmy Carter, the United States has channeled more than $2 billion to the Afghan guerrillas--the largest covert military aid effort ever mounted by the CIA. Saudi Arabia has contributed a roughly equal amount, administered largely by the CIA as well, officials said.

Costs on the Soviet side were far higher. U.S. intelligence estimates put the Soviet contribution at up to $3 billion a year and Soviet troop strength in Afghanistan as high as 115,000.

In Washington, Sen. Richard G. Lugar (R-Ind.) said Moscow’s decision to halt military aid to Afghanistan, together with earlier moves to recognize the independence of the Baltics and withdraw troops from Cuba, clears away major barriers to U.S. economic aid to the Soviet Union.

“It’s very difficult to think of American aid going in the front door and going out the back door to Cuba or Afghanistan,” said Lugar, a senior member of the Senate Foreign Relations Committee.

Times staff writers Mark Fineman, in Kabul, Afghanistan, and William J. Eaton, in Washington, contributed to this story.

Latest Developments

Here’s what happened Friday in the Soviet Union:

WEAPONS FREEZE. The Soviet Union and the United States agreed to halt all military aid to the warring factions in Afghanistan as of Jan. 1, opening the way for a negotiated end to a 12-year civil war that has cost more than a million lives.

ON STRANGE TURF. Secretary of State James A. Baker III ventured into the once-forbidden vastness of KGB headquarters to receive a warm welcome, an offer from the new Soviet spy chief to end the espionage war and an appeal to the CIA to help reorganize its former archrival.

BUTTON, BUTTON. President Mikhail S. Gorbachev, alarmed by the control that rebel officials had of the Soviet nuclear arsenal during the conservative coup last month, has ordered a review of the country’s strategic command system and new safeguards against another takeover of the weapons.