historic references from declassified information from various sources here.
I was in US around that time period. I was a grad student (or early post-doc) around that time and knew some of the people mentioned in the article above. I may put some of my thoughts and perspective, as I remember them now, later but let me put some documents with the link here for experts...
(Some excerpts are there)
Various recent intelligence reports
>State Department cable to Embassy New Delhi, 6 January 1972, Secret
A Concerted Effort by India to Conceal Preparations May Well SucceedFor years, the U.S. intelligence establishment had been monitoring India's nuclear program for signs of a decision to produce nuclear weapons, but in late 1971 and early 1972 it had to consider the possibility that a nuclear test was impending. Recently collected intelligence about an imminent test led the State Department to send a query to the U.S. Embassy in India for its assessment.
State Department Bureau of Intelligence and Research Intelligence Note, "India to Go Nuclear?" 14 January 1972, Secret
"India's Nuclear Intentions," 21 January 1972, Secret,Before the Embassy sent a full response, a team of analysts at the State Department's Bureau of Intelligence and Research produced their evaluation of varied report about India's nuclear intentions: that it would test a device that month, sometime in 1972, or that the government was undertaking a program to test a "peaceful nuclear explosive." According to INR, India had the capability to produce some 20-30 weapons, and it could easily test a device in an underground site, such as an abandoned mine, that would be hard to discover.
Memorandum from Ray Cline, Director, Bureau of Intelligence and Research, to Director of Central Intelligence Richard Helms, enclosing "Possibility of an Indian Nuclear Test," 23 February 1972, SecretEmbassy identified a number of reasons that made it unlikely that India would a test a nuclear device in the coming weeks, but saw "straws" suggesting an underground test "sometime in future." For example, the Government of India had publicly acknowledged ongoing work on the problem of safe underground testing . Moreover, India might have an interest in making its nuclear capabilities known to "enemies." Whatever the Indians decided, external pressure would have no impact on a highly nationalist state and society: "we see nothing US or international community can presently do to influence GOI policy directions in atomic field."
U.S. Embassy Canada cable to State Department, "India's Nuclear Intentions," 7 March 1972, SecretAt the request of Undersecretary of State John Irwin, INR prepared an assessment which included a detailed review of Indian's nuclear facilities and their capacity to produce weapons-grade plutonium as well as capabilities to deliver nuclear weapons to target. While India had signed agreements with Canada and the United States that nuclear reactors were to be used for peaceful purposes, the Indians were likely to claim that an explosive device for "peaceful" purposes was consistent with the agreements. Whether the Indians were going to test in the near future was in doubt. INR could not "rule out" one in the near future. Further, the "strongest incentive [to test] may well be the desire for the increased status of a nuclear power."
Unlikely to Test in the "Near Future" -- State Department cable to U.S. Embassy Ottawa, "Indian Nuclear Intentions," 9 March 1972, SecretWith With Canada's role as a supplier of nuclear technology, including the CIRUS research reactor, senior Canadian officials had close working relationships with their Indian counterpart. James Lorne Gray, the chairman of Canada's Atomic Energy Board, had recently visited India and U.S. embassy officials interviewed him closely on his thinking about Indian nuclear developments. Having spoken with Homi Nusserwanji Sethna, Chairman of the Atomic Energy Commission, and other officials, Gray believed that Sethna opposed a test and that as long as Sethna and Indira Gandhi were in office "there was no chance" that India would test a nuclear device, which would take three to four years to prepare. Gray was mistaken, but was correct to declare that if a decision to test was made, Sethna would "undoubtedly" head the project.
No Technical or Fiscal Obstacle to a Test --U.S. Embassy Canada cable 14 March 1972, SecretState Department officers were also consulting with their counterparts at the Canadian embassy in Washington. During a discussion with the embassy counselor, country desk director David Schneider opined that Indian was unlikely to test a device in the "near future" but he wanted Ottawa's prognosis. Schneider was also interested in whether the Soviets, with their close relationship with India, might be able to use their influence to "deter" a test. If India tested, the U.S. could respond with a "strong statement," but whether "punitive" measures would be taken would depend on whether the test "violated existing agreements."
Leaving Their Options Open" - cable U.S. Embassy Canada, 24 March 1972, SecretElaborating on his earlier cable and responding to the general issues raised by the Department's 9 March message, science attaché Hudson questioned Gray's evaluation of Sethna, suggesting that by combining "guile" and "technical proficiency," the latter could easily have "easily misled" the Canadian. Based on consultations with a variety of Canadian insiders with knowledge of and experience with the Indian nuclear program, the Embassy saw no technical or fiscal barriers to an Indian test. Moreover, any pressure on India not to test would increase the "likelihood" of that happening.
British See No Evidence of a Decision -U.S. Embassy United Kingdom 7 April 1972Further discussions with the Canadian embassy counselor disclosed Ottawa's view that it had no evidence of Indian intentions to test a nuclear weapon or a PNE. The Indians were "leaving their options open." If they decided to test, however, it would be "impossible" for them to move forward "without revealing some indication of their intentions."
"Apparent Reliability and Seeming Credibility" - To U.S. Embassy United Kingdom 22 April 1972The British Government was taking the same view as the Canadians, seeing no evidence that the Indians had made a decision to test, although they had the "capability."
"The Indians Have Decided to Go Ahead" (All around June 20, 1972)The Canadian embassy had asked the State Department for information on the intelligence reports from earlier in the year that an Indian nuclear test was "imminent." The State Department denied the request, but informed the Canadians that the reports were so numerous and their "congruity, apparent reliability, and seeming credibility" so striking that it had become necessary to update official thinking about Indian intentions.
(This group of telegrams discloses that one Japanese diplomat made a good guess ... "Indians have decided to go ahead with a nuclear test" which could occur at "any time;" The Thar Desert in Rajasthan would be the test site....!!! - Americans doubted all the info)
Japanese Views Regarding Indian Nuclear Plans
Japanese-Pakistani Conversations Regarding Indian Nuclear Plan
More on Japanese Views Regarding Indian Nuclear Plans
Next: Some memos of Dr K to Nixon, more in 1973 and 1974...Some personal reflections...
(