Though the United Nations condemned the human rights violations during and following Operation Searchlight, it failed to defuse the situation politically before the start of the war.
Following Sheikh Mujibur Rahman's declaration of independence in March 1971, India undertook a world-wide campaign to drum up political, democratic and humanitarian support for the people of Bangladesh for their liberation struggle. Prime Minister Indira Gandhi toured a large number of countries in a bid to create awareness of the Pakistani atrocities against Bengalis. This effort was to prove vital later during the war, in framing the world's context of the war and to justify military action by India. Also, following Pakistan's defeat, it ensured prompt recognition of the newly independent state of Bangladesh.
Following India's entry into the war, Pakistan, fearing certain defeat, made urgent appeals to the United Nations to intervene and force India to agree to a cease fire. The UN Security Council assembled on 4 December 1971 to discuss the hostilities in South Asia. After lengthy discussions on 7 December, the United States made a resolution for "immediate cease-fire and withdrawal of troops". While supported by the majority, the USSR vetoed the resolution twice. In light of the Pakistani atrocities against Bengalis, the United Kingdom and France abstained on the resolution.
On 12 December, with Pakistan facing imminent defeat, the United States requested that the Security Council be reconvened. Pakistan's Deputy Prime Minister and Foreign Minister, Zulfikar Ali Bhutto, was rushed to New York City to make the case for a resolution on the cease fire. The council continued deliberations for four days. By the time proposals were finalised, Pakistan's forces in the East had surrendered and the war had ended, making the measures merely academic. Bhutto, frustrated by the failure of the resolution and the inaction of the United Nations, ripped up his speech and left the council.
Most UN member nations were quick to recognise Bangladesh within months of its independence.
As the Bangladesh Liberation War approached the defeat of the Pakistan Army, Bhutan became the second country in the world (after India) to recognize the newly independent state on 6 December 1971. Sheikh Mujibur Rahman, the first President of Bangladesh visited Bhutan to attend the coronation of Jigme Singye Wangchuck, the fourth King of Bhutan in June, 1974.
USA and USSR
Senator Ted Kennedy led congressional support for the liberation of Bangladesh
Bob Dylan took part in the Concert for Bangladesh at Madison Square Garden in New York, August 1971
The Nixon administration was widely criticized for its close ties with the military junta led by General Yahya Khan. American diplomats in East Pakistan expressed profound dissent in the Blood telegram
The United States supported Pakistan both politically and materially. US President Richard Nixon denied getting involved in the situation, saying that it was an internal matter of Pakistan, but when Pakistan's defeat seemed certain, Nixon sent the aircraft carrier USS Enterprise to the Bay of Bengal, a move deemed by the Indians as a nuclear threat. Enterprise arrived on station on 11 December 1971. On 6 and 13 December, the Soviet Navy dispatched two groups of ships, armed with nuclear missiles, from Vladivostok; they trailed US Task Force 74 in the Indian Ocean from 18 December until 7 January 1972.  Nixon and 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 which 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. 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 and routed 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.
The Soviet Union supported Bangladesh and Indian armies, as well as the Mukti Bahini during the war, recognising that the independence of Bangladesh would weaken the position of its rivals – the United States and China. It gave assurances to India that if a confrontation with the United States or China developed, the USSR would take countermeasures. This was enshrined in the Indo-Soviet friendship treaty signed in August 1971. The Soviets also sent a nuclear submarine to ward off the threat posed by USS Enterprise in the Indian Ocean.
At the end of the war, the Warsaw Pact countries were among the first to recognise Bangladesh. The Soviet Union accorded recognition to Bangladesh on 25 January 1972. The United States delayed recognition for some months, before according it on 8 April 1972.
As a long-standing ally of Pakistan, the People's Republic of China reacted with alarm to the evolving situation in East Pakistan and the prospect of India invading West Pakistan and Pakistani-controlled Kashmir. Believing that just such an Indian attack was imminent, Nixon encouraged China to mobilise its armed forces along its border with India to discourage it. The Chinese did not, however, respond to this encouragement, because unlike the 1962 Sino-Indian War when India was caught entirely unaware, this time the Indian Army was prepared and had deployed eight mountain divisions to the Sino-Indian border to guard against such an eventuality. China instead threw its weight behind demands for an immediate ceasefire.
When Bangladesh applied for membership to the United Nations in 1972, China vetoed their application because two United Nations resolutions regarding the repatriation of Pakistani prisoners of war and civilians had not yet been implemented. China was also among the last countries to recognise independent Bangladesh, refusing to do so until 31 August 1975.