Planned sale of US computer to India points up snags in relations. Some Americans fear the technology could fall into Soviet hands

A lightening-fast computer that can predict weather or design nuclear weapons has come to symbolize struggling relations between the United States and India. After a year-long deadlock, American and Indian negotiators reached a tentative agreement earlier this month on safeguards for sale of a $15 million supercomputer to India. It would be the first purchase by a non-Western nation of such sensitive technology.

Officials on both sides, however, say the deal is far from certain. India says it wants at least two of the computers to forecast the unpredictable behavior of the summer monsoon rains.

But despite President Reagan's pledge last year to sell high-technology items to India, many officials in Washington continue to view the idea with suspicion. They worry that the supercomputer technology will fall into the hands of the Soviet Union, India's major arms supplier, in spite of Indian reassurances to protect the technology. And they question whether the machines will be used for defense purposes, possibly against Pakistan, the US's main ally in South Asia.

``It's a sensitive issue selling a supercomputer to a country that's not an ally,'' says Bhabani Sen Gupta of the Center for Policy Research, an independent think tank here. ``This would be a significant departure in American foreign policy.''

Although details of the tentative pact remain secret, it is widely held that the US is no longer insisting that Americans be allowed to operate the computer or make surprise inspections. India had opposed such protection proposals, contending that they infringe on its sovereignty.

That concession could face tough opposition in Washington, sources close to the negotiations say. Though the State Department wants to improve relations, the sale could be sidetracked by Pentagon hard-liners opposed to closer ties, Indians say. In addition, they worry that a supercomputer decision could be delayed by the disarray in the Reagan administration over the Iran arms controversy.

Another roadblock is the issue of picking a machine. The Indians want the latest models, including those made by Cray Research Corp. and Control Data Corp. Because of the impasse over the purchase, India has also shown interest in a Japanese model. In November, the US and Japan agreed on ground rules for competing over the sale - although Washington has recently complained that the Japanese are not complying with the pact.

India says it is not interested in older supercomputer technology that some US officials are more willing to sell here.

``If they're throwing it into the garbage pit, we're not going to pull it out,'' says N. Seshagiri, who heads computer development for the Indian government.

The supercomputer purchase is also controversial within India. Critics question whether the machine is needed and challenge Prime Minister Rajiv Gandhi's plans to modernize by importing Western technology. But officials say the computer will spare Indians from the vagaries of the monsoon, which brings rain to parched lands in midsummer. But sometimes the rains hit with unexpected ferocity, causing flooding that takes a toll on people, livestock, and crops.

By analyzing data from weather satellites and ground stations, the supercomputer can produce an accurate 10-day forecast in five hours. Less powerful machines take more than 150 hours. The computer also would be used for gathering agricultural and health information.

The supercomputer can devise software to use in speeding up the operation of slower computers. If examined, such software could reveal the makeup of the faster machine. In addition, the supercomputer can design nuclear weapons, break top secret codes, and even simulate nuclear war. These capabilities could have a grave impact on a region in which India already has exploded a nuclear device and Pakistan is reported to be close to doing so, US officials say.

The computer's sale will be a crucial test in US-Indian ties, observers say. Since Mr. Gandhi's visit to Washington a year and a half ago, the US has boosted trade and business investment here in hopes of overriding political differencs that have kept the two countries apart.

US officials predict US business investment of $500 million will jump by 30 percent next year. They also have announced steps to help India develop its defense industries. But the recent US proposal to sell airborne-warning-and-control-system (AWACS) aircraft to Pakistan has once again soured relations with India. Refusal to sell the supercomputer would be another serious setback.