India's "landmark" first successful nuclear test in 1974 was a setback for its relations with the US that were on the mend since their 1971 nadir over the Bangladesh war, says a new US document.
The test amplified US concerns about then prime minister Indira Gandhi's close relationship with the Soviet Union and her decision to develop nuclear technology while dependent on US food aid.
The India-Pakistan War of 1971 cast a long shadow and defined the US relationship to both countries during the presidencies of Richard Nixon and Gerald Ford, says the publication brought out by the State Department's Office of the Historian.
The chief concerns of the US were the enforcement of the 1972 Simla Agreement and the re-establishment of normal relations between India and Pakistan, says the publication in the State Department's Foreign Relations series.
Bilateral relations with India improved considerably from their 1971 nadir until the 1974 Indian nuclear test, says the publication documenting important US foreign policy decisions and actions in South Asia in 1973-1976.
Nixon's appointment of Daniel Patrick Moynihan as Ambassador to India in 1973 led to the resolution of several long-standing economic and political tensions, although New Delhi continued to object to US support for Pakistan and alleged a US role in its domestic instability, it said.
But "India's successful nuclear test was a setback for bilateral relations, amplifying US concerns about Indira Gandhi's close relationship with the Soviet Union, her declaration of martial law in 1975, and her decision to develop nuclear technology while dependent on US food aid," it said.
The documents on India and Pakistan are combined into two chapters covering US relations with both countries, with the landmark Indian nuclear weapons test of May 1974 as a point of division.
Relations between the US and Pakistan were generally good, with President Zulfikar Ali Bhutto visiting Washington in February 1975, said the publication.
Nevertheless, US policymakers remained anxious about Pakistani instability following the 1971 war, and about Bhutto's viability as a national leader.
Washington was also concerned about Bhutto's attempts to quell domestic regional disturbances, particularly in Pakistan's northwestern frontier provinces, and to establish his legitimacy as a nationalist and populist reformer.
Nevertheless, President Nixon's policy of providing military and economic support to Pakistan was continued during the Ford administration.
In Bangladesh, the US also sought to establish solid diplomatic relations with a new government, that of Prime Minister Mujibur Rahman, while seeking to limit the influence of other regional powers over the desperately impoverished country by providing food and development aid.
The US relationship with Dhaka was complicated by Bangladeshi suspicion of US motives, as well as by the 1975 overthrow and murder of Mujib, followed by the establishment of a military regime.
In Afghanistan, the major event was the dissolution of the monarchy and its replacement by the republican government of Mohammad Daoud, the new volume said.
The change in regime did not cause an alteration in US policy, which, as in the past, attempted to offset Soviet influence in Afghanistan with diplomatic support and development assistance, it said.
The Nixon administration quickly recognised the new Afghan government and continued to provide it with development aid and opium eradication assistance, while mediating the continual Afghan dispute with Pakistan over both countries' Pushtun borderlands.
In dealing with Sri Lanka, the Nixon and Ford administrations found the US relationship with prime minister Sirimavo Bandaranaike complicated by the latter's presidency of the Non-Aligned Movement, as well as her continued attempts to establish an Indian Ocean Peace Zone and her criticism of the US expansion of the British base at Diego Garcia.
At the same time, US policymakers attempted to assess and contain the expanding Soviet naval presence and influence in the Indian Ocean.
The documents provide detailed coverage of the Nixon and Ford administrations' relations with Nepal and Bhutan, the first such coverage in the Foreign Relations series since the volumes covering the Eisenhower administration.