CALCUTTA.-The independence struggle in East Pakistan is drawing the United States, the Soviet Union, Communist China and India into a sort of diplomatic minuet and maneuver with considerable potential consequences. What these ,countries eventually decide to do could determine not only the outcome of the war but also the future course of South Asia.

The process promises to be a long-drawn-out one. The autonomy drive of the Bengali population of East Pakistan could conceivably last for years. It could plunge the entire Indian subcontinent into turmoil, particularly if it turns into a Maoist or similar insurgency.

The reaction so far of the major powers affected by the insurgency has gone something like this:

RUSSIANS CRITICAL

The Russians, the first to speak, sharply criticized the Pakistani Government in West Pakistan and called for an immediate end to the "repressive measures and bloodshed." Pakistan responded curtly by saying that this was an internal matter and by telling the Russians in effect, to mind their own business.

A week after the Moscow move, communist China, which has been wooing Pakistan in an effort to counterbalance Russia's influence in India, publicly took sides with the Pakistani Government. The Chinese praised President Yahya Khan for taking "the relevant measures," and charged that the United States and the Soviet Union "working in conjunction with the Indian reactionaries, crudely interfered in the internal affairs of Pakistan."

The United States at first took a cautious stance, saying that, if the Pakistani Government sought humanitarian assistance for those suffering in East Pakistan, Washington would respond. This was essentially an echo of the position taken earlier by U Thant the United Nations Secretary General. But Pakistan rejected the idea of humanitarian assistance from others, and turned back a Red Cross relief plane that had come to Karachi with the intention of flying on to Dacca, the East Pakistani capital.

As press and other reports mounted about the widespread killings of Bengali civilians by the Pakistani Army, Washington expressed concern about the army's use of previously supplied American arms and about the loss of life. The State Department said it was reviewing its entire aid program to Pakistan.

India, which has fought two wars over Kashmir with Pakistan and a border war with China, has denounced the Pakistani action as "medieval butchery" and "systematic genocide" of the Bengalis, and has rejected the notion that the strife is an internal Pakistani matter.

Many observers believe that India, which is already giving some assistance, on an unofficial basis, to the Bangla Desh (Bengal Nation) rebel force, may have to declare herself soon and provide direct aid in significant amounts.

Some Indian Army officials are itching to pin back the Pakistanis' ears in this crisis and the possibility of another Indian-Pakistan war cannot be entirety ruled out. All it would take would be one irrational military act.

Most diplomats here view the Chinese pledge of support to Pakistan as a pro forma move-more bluster than a real military threat against Pakistan's critics. But at this euphoric moment of improving relations between Washington and Peking, it might be enough to make Washington think longer about coming down hard against Pakistan and risking a diplomatic blow-up with the Chinese.

Another explanation offered is that the American stance simply reflects its two decades of support of Pakistan's military governments with billions of dollars in military and economic aid. Many of those in the State Department who endorsed this policy find it difficult now to admit, as some critics charge that, on balance, it was a failure, that it fostered development only in West Pakistan and left East Pakistan a badly treated poor relation, it was this situation that helped fuel Bengali bitterness and led to the present crisis.

Foreign aid is a key factor in this crisis. Should the World Bank, the United States and the 10 other Western countries in the aid-Pakistan consortium refuse to make any future commitments and reject Pakistan's requests to delay the payment of existing loans, Pakistan would probably be compelled very quickly to pull its army out of East Pakistan and bring it home-a 1,000-mile trip across Indian territory.

The Russians and the Chinese, both of whom have been providing Pakistan with military aid in recent years do not seem to have the same fence-straddling problems as the Americans.

The Russians, in taking the Bengali side have apparently decided that Pakistan is an extremely sick country, that India is the important power in this region and the power to line up with.

The Chinese have apparently decided that whatever the Russians and Indians support, they must oppose. Some analysts think the Chinese may have blundered by turning their backs on the Bengali independence movement for reasons of power politics.

Few Bengalis understand all this world diplomacy. They know only that no one has recognized their new government.