President Carter's special emissary to India, Clark Clifford, defended arms aid to Pakistan today as a necessary signal to the Soviet Union not to try to extend its writ beyond Afghanistan and said any Soviet move toward the Persian Gulf "means war."

By direct aid and encouraging other nations to aid Pakistan to defend its northern and western borders against Soviet forays, Clifford said, "what we hope to do is send them such a strong signal that they will not go further."

Clifford would not disclose details of his 75-minute conversation with Indian Prime Minister Indira Gandhi, who has sharply criticized resumption of U.S. arms aid to the Pakistanis.

India, which enjoys a close relationship with the Soviet Union, has said it believes the Soviets when they say they will withdraw their troops from Afghanistan and has labeled the Soviet intervention an "internal" Afghan matter.

"The goal of our two governments is exactly the same -- to have the Soviets withdraw their troops from Afghanistan," Clifford said in a press conference. He acknowledge, however, that the Indians "do not believe that the United States approach constitutes the most effective approach."

"The Indian government believes that negotiation, positive persuasion, might be more effective," he said.

According to a Foreign Ministry spokesman, Gandhi told Clifford that India was against foreign intervention in any country and said the de-escalation was essential to ensure the withdrawal of Soviet troops from Afghanistan. Foreign Minister P. V. Narasimha Rao, the spokesman said, called for all countries involved to act circumspectly in order to defuse the crisis.

At a dinner tonight in honor of visiting Austrian Chancellor Bruno Kreisky, Gandhi said detente was being abandoned by the world's rival powers, leading to fears of a third world war, and the theater of conflict no longer was Europe but Asia.

"We feel the reverberations and hear the clash of rival powers around us. Nations are being asked to stand up and be counted, as if partisanship were the test of rectitude," Gandhi said.

She warned rival powers in the world to keep their hands off the troubled regions, declaring that India "is not amenable to manipulation."

Clifford said that the relationship between the Indian and Soviet governments, which signed a friendship pact in 1971, "might be very useful. It is our hope that the Indian government may be able to be helpful in persuading the Soviets to get their troops out of Afghanistan."

The Indian and U.S. governments, however, have widely differing views on the reasons for the Soviet troops' intervention in Afghanistan. Speaking in the lower house of Parliament Wednesday, Gandhi repeated her assertion that the troops had been invited in by deposed president Hafizullah Amin.

Clifford today characterized the Soviets' "brutal entry" as the culmination of a long buildup in the Indian Ocean, Arabian Sea and the Horn of Africa, while the United States "wondered what is afoot." If there is no response to such aggression. he said, "the temptation to go on with it is irresistible. The president does not intend that we make that mistake this time."

The Afghanistan invasion, Clifford said, marked the first time the Soviets had put troops outside the Warsaw Pact area and "constitutes a dramatic and decided departure from previous Soviet policy.

"What is the danger that the Soviet Union sees in the direction in which they have gone into Afghanistan?" he asked rhetorically. "They know there is no danger to the Soviet Union in that area.

"What we do see is that the Soviet move into Afghanistan brings them within 300 miles of the Persian Gulf," he said.

Clifford said Carter was sending the Soviets a "message" in his pledge to use military force, if necessary, to protect the Persian Gulf.

"The message is: they must know that if part of their plan is to move toward the Persian Gulf, that means war.

"We also want to get the message to them that if there is any temptation on their part to move over into Pakistan, that will mean also grave difficulties."

Acknowledging India's concern about the arming of Pakistan, Clifford said it was "in the interests of peace" for the United States to provide "modest amounts" of defensive arms that will not upset the Indo-Pakistan military balance.

"We know that is not a popular move with the Indian government," he said. "Yet the gravity of the threat is such that we believe it is an appropriate policy for us to follow."

Zbigniew Brzezinski, President Carter's national security adviser, arrives in Islamabad, Pakistan, Friday for talks that Pakistan's military rulers hope will lead to a defense link with the United States.