As fresh Soviet divisions were reported rolling into Afghanistan, the United States made new decisions yesterday to show displeasure by cutting back a broad range of official and cultural ties with the Soviet Union.

Among the links to be affected is the U.S.-Soviet cultural exchange agreement, which provides for the exchange of monthly magazines, large-scale exhibitions, theatrical performances, teachers, students and other private citizens. Officials said the United States will halt negotiations on an extension of the pact, which terminated Dec. 31.

Some relatively inconspicuous cultural and educational exchanges may proceed on a case-by-case basis for now, officials said. But it was expected that even these will be affected if the freeze in Soviet-American relations is on long duration.

Th report on Soviet reinforcements, by State Department spokesman Hodding Carter, suggested that this foreign presence in Afghanistan will become large and possibly "permanent."

Carter said one or two more Soviet infantry divisions, totaling 20,000 to 25,000 troops, recently moved to the Afghan border and may have crossed by now, augmenting 50,000 to 60,000 Soviet troops already in that country.

In a portent of still further reinforcement Carter added that the United States had indications that tow or three additional Soviet ground force divisions -- more than 30,000 men -- may be mobilizing north of the border.

For the first time, U.S. officials comment went beyond a report on the continuing Soviet influx to speculation about its long-term purpose. Carter said that the extent and nature of the equipment that "there is nothing expeditionary" about the Soviet force but that it is probably the core of a larger, permanent force to be deployed in the future."

Behind his conclusion, according to official sources, is intelligence that the Soviets are well along in the process of building a major combined force in Afghanistan, with ground forces, airborne units, engineer and support troops and combat aircraft.

Several squadrons of Mig and Sukhoi jet fighters have been stationed near Kabul and in susidiary airfields, according to U.S. officials Soviet anti-aircraft equipment is being brought in, evidently to protect headquarters being established, the sources said.

The report of a larger and potentially permanent Soviet presence came as President Carter invited more than 100 members of Congress to the White House for a buffet dinner and briefing tonight about recent U.S. countermeasures against the Soviet Union.

The White House said it invited members of the Senate Foreign Relations and House Foreign Affairs committees and the Agriculture committees of both houses, as well as lawmakers from areas particularly affected by the restrictions on trade with the Soviet Union. Because Congress is not in session, officials had no estimate of the number of legislators who will attend.

Details of the U.S. countermoves are still being ironed out in executive branch meetings. A government-wide coordinating committee on U.S. relations with the Soviet Union is to establish some of the new policies in a meeting scheduled for today.

Under guidelines to be established, according to officials, the United States will place and indefinite moratorium on high-visibility visits or exchanges with the Soviet Union. Most trips involving officials of the rank of assistant secretary and above will be barred. The exceptions will be visits for purposes deemed to be of overriding national importance, such as arms control discussions.

Officials expected that the exchange of parliamentarians and other officially sponsored leaders also will be halted indefinitely, though such visits are not under the control of the executive branch.

Still under consideration is a reduction in the Soviet diplomatic presence in the United States, which almost certainly would prompt a retaliatory Soviet cutback in the U.S. presence in Moscow. A tentative decision to cut the number of Soviet diplomats here reportedly has been reversed temporarily by a plea to the president from Thomas J. Watson Jr., the U.S. ambassador to Moscow.

Another aspect of the U.S. response to the situation in Afghanistan is renewed military and economic assistance to that country's neighbor, Pakistan. rPresident Carter, in an interview with NBC, said last night that the United States is helping form an international "consortium" to provide Pakistan with military assistance.

Carter said the plan is "still in the embryonic stage," subject to negotiation with Pakistan and donor nations, possibly including some from the oil-rich Middle East. He also said the U.S. contribution would require congressional approval.

U.S. aid to Pakistan was halted in April, under laws intended to prevent the spread of nuclear weapons, because of intelligence information that Pakistan is building a plant to make material for atomic weapons.