The United States supported Pakistan both politically and materially. Nixon, backed by Henry Kissinger, feared Soviet expansion into South and Southeast Asia. Pakistan was a close ally of the People's Republic of China, with whom Nixon had been negotiating a "rapprochement" and where he intended to visit in February 1972. Nixon feared that an Indian invasion of West Pakistan would mean total Soviet domination of the region, and that it would seriously undermine the global position of the United States and the regional position of America's new tacit ally, China. In order to demonstrate to China the "bona fides" of the United States as an ally, and in direct violation of the US Congress-imposed sanctions on Pakistan, Nixon sent military supplies to Pakistan, routing them through Jordan and Iran, while also encouraging China to increase its arms supplies to Pakistan.

The Nixon administration also ignored reports it received of the 'genocidal' activities of the Pakistani Army in East Pakistan, most notably the Blood telegram. When Pakistan's defeat in the eastern sector seemed certain, Nixon sent the USS "Enterprise" to the Bay of Bengal, a move which was a nuclear threat. The "Enterprise" arrived on station on December 11, 1971. On 6 December and 13 December, the Soviet Navy dispatched two groups of ships, armed with nuclear missiles, from Vladivostok; they trailed U.S. Task Force 74 into the Indian Ocean from 18 December 1971 until 7 January 1972. The Soviets also sent a nuclear submarine to ward off the threat posed by USS "Enterprise" in the Indian Ocean.

American policy towards the end of the war was dictated primarily by a need to restrict the escalation of war on the western sector to prevent the 'dismemberment' of West Pakistan. Years after the war, many American writers criticized the White House policies during the war as being badly flawed and ill-serving the interests of the United States.

The Soviet Union sympathized with the Bangladeshis, and supported the Indian Army and Mukti Bahini during the war, recognizing that the independence of Bangladesh would weaken the position of its rivals - the United States and China. The USSR gave assurances to India that if a confrontation with the United States or China developed, it would take counter-measures. This assurance was enshrined in the Indo-Soviet friendship treaty signed in August 1971.

India
American and Soviet involvement
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