NEW DELHI.-The Indians, with strong sympathies for the month-old Bengali independence struggle in East Pakistan, are trying to keep their balance on a diplomatic tightrope, buffeted by a heavy wind.

Despite its denunciations of the Pakistani Army's offensive against the independence movement, New Delhi has so far refrained from recognizing the new government of Bangla Desh, or Bengal nation, proclaimed by the East Pakistani independence movement.

There are two basic reasons for this restraint, One is the desire to avoid having another war with Pakistan, although India's military strength is superior and independent observers believe India would quickly win such a war.

The other reason, perhaps the more important at this stage, is concern that recognition of Bangla Desh now might tend to substantiate, in the eyes of the world, the Pakistani charge that this has been at the bottom of the Indian-Pakistani dispute and that the Bengali insurgents are essentially Indian puppets.

India is at present embroiled with Pakistan in a diplomatic feud over the repatriation of Indian diplomats in Dacca, the capital of East Pakistan, who want to return home, and the repatriation of East Pakistani diplomats in India who do not, because they have sworn allegiance to the independence movement. But the immediate issue is military, not diplomatic. The Bangla Desh forces badly need arms and training, if they are to carry out effective guerrilla warfare to dislodge the better-equipped Pakistani Army. Some Indian assistance has already been channeled to the Bengalis, but it has been done on an unofficial basis and it has not so far been on a large scale.

Indian officials recognize privately that merely to sit back and wait to see what happens in the civil war could be a self-fulfilling negative strategy. Without some significant help now, ,the Bengali struggle, although not likely to crumble, will take much longer to achieve significant results and in the process might turn away from its moderate leadership and become a militant leftist insurgency.

So the likelihood, according to authoritative Indian sources, is for increased aid to the Bengalis-still on an unofficial basis- but no commitment of Indian fighting troops.

Such increased aid would include not only ammunition, arms (presumably without Indian markings), food and transport, but also training-which the Bengalis sorely need, since no more than 12,000 to 15,000 of them are regular soldiers who have fled from the Pakistani Army.

But even if all this is done through unofficial channels, it will put an increasing strain on Indian "neutrality". With Indian public opinion growing more and more pro-Bengali and more and more anti-Pakistani, and with strong pressures for recognition of the new Bengali independence regime within her own Government, Prime Minister Indira Gandhi will have to use a firm hand to maintain India's present restrained posture.

At the same time, reliable informants say, Mrs. Gandhi is sharply aware that India is the only likely source of help now for the Bengalis, and that West Bengal State's 700-mile border with East Pakistan provides the easiest access corridors for supplies to the insurgents.

The Indian roads leading north from Calcutta to points along the border already look like a supply route. Bengali trucks can be seen heading into Indian towns for fresh supplies-carrying empty fuel drums and ammunition boxes.

Bengali independence forces have set up camps near Indian border posts, which probably explains some of the brief shooting incidents recently between Indian and Pakistani troops.

In Calcutta, capital of West Bengal State, there are many stories of new instances of Indian military assistance.

One report is that Indian munitions factories are turning out weapons and ammunition without Indian markings. Another is that Indian officers accompanied a large Bengali guerrilla force on a raid last week on a Pakistani Army garrison at Navaran, on the road to Jessore.

The Indian Government denies all such reports, but in discussing some of them Indian officials privately offer alternative explanations. One is that some former Indian Bengali officers - given emergency commissions for the 1962 border war with Communist China and the 1965 Kashmir war with Pakistan, but since retired-may have joined up with the East Pakistani Bengalis. By their language and appearance they could not be told apart.

And some Indian officials tell their friends that if the East Pakistanis come across the border seeking arms and training, "they will find ways to get them."

"LOCAL HELP" OBTAINED

East Pakistani insurgent leaders insist that they are getting very little from the Indian Government. They always add, however, that they are receiving a lot of "local help."

According to authoritative sources, India wants to wait-perhaps some months before deciding on recognition of Bangla Desh. Mrs. Gandhi is said to want to see what will happen when the monsoon rains set in heavily in a few weeks and the Pakistani Army's heavy armor bogs down in the mud, forcing a lull in its offensive.

What she wants to find out, these sources say, is whether the Bengalis can mount a reasonably effective guerrilla campaign or whether the independence movement's leaders will weaken and accept some kind of Pakistani political settlement, perhaps made through a foreign country-In other words, whether the Bengalis are determined to see this struggle through to the end.

New Delhi is also sounding out other governments, hoping that someone else will recognize Bangla Desh first, to take the sting out of Pakistan's charge that this is an Indian plot.

But such countries as the United States are waiting to see what India does, on the ground that India is the country most directly affected by this crisis. What this means is that India herself will probably have to take the lead eventually on the East Pakistani Issue.