In a scene resembling a giant figure eight, one loop red and the other blue, Pakistani porters trudge a quarter of a mile with boxes of grapes on their heads to the dividing line between India and Pakistan, where they shift their loads to the heads of waiting Indians.

The gaily painted and tinsled trucks that carry goods in this part of the world are forbidden to come up to the border, let alone cross it. So a human conveyor belt, one half on the Pakistani side the other half in India, is used to make the transfer.

Moreover, the porters, who look alike and speak the same language, wear different-colored tunics to make sure no one sneaks across the border.

This time-consuming and unwieldly transfer of fresh fruit illustrates the deep and abiding mutual distrust that pervades all relations between India and Pakistan.The South Asian neighbore have fought three wars in the almost 33 years since they were created from British India and given their independence.

"You don't understand," said one well-educated Indian at a New Delhi dinner party recently. "Pakistan is our enemy." The same comment about India is heard frequently from educated Pakistanis.

Official efforts to bridge this chasm, which has been widened by the Soviet invasion of Afghanistan in December, will continue when Pakistani Foreign Minister Agha Shahi visits New Delhi Tuesday for talks with his Indian counterparts, who made two trips to Islamabad earlier this year.

But attempts to normalize relations between the two neighbors appear likely to take a backseat to their differences over Afghanistan and what each feels is its need to bolster its military defenses.

A senior Pakistani diplomat in New Delhi signaled those differences in a unusually candid interview in which he accused the Indians of exhibiting "a lack of will" to pressure the Soviets to withdraw from Afghanistan. He also criticized what he called India's "obession in preventing the supply of arms of Pakistan" while signing a $1.6 billion deal to buy sophisticated weapons from the Soveit Union.

"The people of Pakistan are not much impressed by the logic demonstrated by India during the past few months, in which the supply of arms by America to Pakistan would have inducted a superpower into the region, but the supply of arms by the Soviet Union to India would not," continued the senior diplomat, who asked that his name not be used.

"This is one of the obstacles to mutual confidence between the two countries," he said.

India's official Foreign Ministry spokesman replied that every time Pakistan received arms, "they were used against us.

The Indo-Pakistani dispute goes beyond mistrust between hostile neighboring nations and takes on the coloration of a family fued. Added to that is the divisiveness of religious prejudice, Pakistan was created as an Islamic nation to keep Moslems from being overwhelmed in Hindu India.

"Pakistan remains about as distant as Shangri-La to the average non-Moslem Indian. It is almost easier for Indians to get British citizenship and green cards in the United States than it is to get a tourist visa to Pakistan," wrote Tavleen Singh in a recent issue of New Delhi magazine.

In the current issue of another Indian magazine, Onlooker, S.M. Abdullah wrote, "The native Pakistani believes that Hindus in India are cannibals who thrive on the flesh of Indian Moslems."

This enmity fuels a conventional arms race that threatens to expand into nuclear weapons, with India capable of building an atomic bomb and Pakistan believed working toward that end. It also provides a field for superpower rivalry, as India has developed close, ties with the Soviet Union over the years while Pakistan considers China its most faithful ally.

The United States, which once played that role with Pakistan, is trying with limited success to be friends with both.

India, whose relations with China are cool, is deeply suspicious of the possibility of a Sino-Pakistani-American arms axis. Despite the sharp Pakistani refusal of a $200 million American arms offer, the Indian Defense Ministry cited in its annual report issued last week "the reported decision of China and the U.S.A. about large-scale arms supplies to Pakistan."

For India, a Pakistani diplomat said, the presence of 100,000 Soviet troops an hour's flight from 1new Delhi is less worrisom than the possibility that the Soviet invation of Afghanistan might lead to Pakistan's getting a new supply of arms.

"India has interposed its influence against the sale of arms to Pakistan in every country of the world, including France and China," the Pakistani diplomat charged.

With the differences so bluntly stated publicly even before the bilateral talks have started, one Western diplomat in New Delhi commented, "I don't see how Agha Shahi's meetings can be a productive exercise. What have they got to talk about that they can agree on?"

The Western diplomat added that the process of normalizing relations has not yet swept away years of mistrust to the point where larger, more powerful India can recognize Pakistan's legitimate security needs.

Despite the differences, the halting process of normalization has gone on for the last eight years, and there is now a vast improvement in the relations between the two countries that is unlikely to be rolled back.

Before 1972 there were hardly any peaceful contacts between India and Pakistan. Things were so restricted that it was impossible to mail a letter between the two countries.

A nine-year trade embargo ended in 1974, and rail and air traffic between the two countries resumed two years later. Last year a Pakistani cricket team visited India for test matches for the first time in more than a decade. According to a diplomat in New Delhi, "More people listened to the cricket matches on the radio than to politicians talking about the problems between the two countries."

Nonetheless, problems remain. There are still no direct airline connections between Islamabad and New Delhi, the two capitals, and it is nearly impossible to make telephone or telex calls from one country to the other. Plane and hotel reservations are made via Hong Kong or London rather than directly.

The one Pakistani journalist stationed in India, for example, cannot travel out of New Delhi without a diplomat accompanying him. And papers in both countries regularly run stories about breaking up spy rings from the other nation.