Alarm bells were set off in the US government toward the end of 1995, when American spy satellites detected a surge of activity at the Pokhran nuclear test facility in northwestern India.
Workers at the site deep in the Thar Desert were observed clearing debris from a 328-foot underground shaft, prompting US officials to suspect that India was readying its first nuclear test blast since 1974.
But when India's new Hindu nationalist government stunned the world this week by testing not one, but three atomic devices, nowhere was the surprise greater than in the US intelligence community.
"We did not know," concedes a US intelligence official. "They took measures to avoid detection. This is something we were monitoring. But if countermeasures are taken, this becomes problematic."
The blasts, which ended 24 years of uncertainty over India's atomic intentions and could fuel a destabilizing regional arms race, re-arranged the global power balance by adding the world's largest democracy to the elite nuclear-weapons club of the US, Britain, China, Russia, and France.
India's success in concealing the test and the sophistication of the devices - one was a thermonuclear bomb - serve as a stark reminder that nations bent on acquiring weapons of mass destruction can hide their programs from even the most advanced surveillance.
Accordingly, many experts worry that India's action may encourage other nations bent on acquiring nuclear, chemical, and biological weapons to follow its lead in pursuing clandestine development programs.
"It is going to make it easier for other countries in due course to say this is acceptable," warns Spurgeon Keany, president of the Arms Control Association, a Washington-based policy institute.
The concern over the ease with which nuclear, biological, and chemical weapons programs may be concealed was last driven home after the 1991 Gulf War. International inspectors sent into Iraq discovered a nuclear weapons program far larger and more advanced than the Central Intelligence Agency or other intelligence services had previously determined.
It was this concern that almost triggered a war between the US and Iraq this year after Iraqi dictator Saddam Hussein blocked United Nations efforts to root out his chemical and biological warfare programs.
And, the same concerns are fueling US apprehensions that Iran, despite its membership in international nuclear, chemical, and biological arms control treaties, is aggressively pursuing the secret development of all three types of weapons systems. Iran denies the charges.
Even when US intelligence detects breaches of nonproliferation regimes (China has allegedly provided technology and knowhow to Pakistan's secret nuclear weapons and missile programs for years) the disclosures can fail to trigger actions that halt the efforts.
That point may be tested soon enough if Pakistan, which has fought India three times since it won independence in 1947, makes good on threats to respond to India's blasts by conducting its first-ever nuclear test explosion. China, which fought a 1962 war with India over a yet-to-be-resolved border feud, might also reconsider its membership in the 1996 Comprehensive Test Ban Treaty (CTBT). Signers of the treaty agree to ban atomic tests for all time.
Critics of multilateral nonproliferation pacts argue that the difficulty of detecting and preempting secret weapons of mass destruction programs render such treaties inoperable. They say the US must take steps to ensure its own security, such as developing new nuclear arms, continuing underground tests to ensure the reliability of the current arsenal, and building a national missile defense system.
More GOP roadblocks
Led by conservative Republicans, these critics fought unsuccessfully to block Senate approval last year of the 1993 Chemical Weapons Convention. They are now mounting an offensive against ratification of the CTBT that could receive a boost from the Indian explosions.
Administration officials and arms control advocates respond that despite the detection and preemption problems, international nonproliferation treaties with tough monitoring regimes make the world a safer place.
They point to the successes in halting nuclear proliferation, including ending South Africa's atomic weapons program and the transfer of weapons-grade uranium in 1994 from Kazakstan to the US.
The Clinton administration contends that it is winning China's compliance with nonproliferation efforts, a topic high on the agenda of next month's summit in Beijing between President Clinton and his Chinese counter-part, Jiang Zemin.
But even arms control advocates acknowledge that better intelligence-gathering by the US and other participants in nonproliferation accords as well as technical agreements - such as the Missile Technology Control Regime - are indispensible in ensuring compliance.
The failure to detect the Indian tests "has tremendous implications for the US intelligence community being asleep at the switch," asserts Jeremiah Sullivan, a University of Illinois physicist and member of the JASONS, a panel of independent advisers to the government on nuclear-arms policy.
"This does not help the CTBT," he continues, noting that the global monitoring systems that the treaty will create will only detect nuclear test blasts after they occur, not before. "The CTBT is a treaty to end nuclear testing. It is not a treaty to do everything," he explains.
Some experts say that to discourage other nations from following India's lead, the US and other countries must take harsh action, including imposing economic sanctions, against New Delhi. There are indications that such advice is being heeded, auguring serious new economic problems for a country mired in grinding poverty.
India's tests "will gain them isolation and retribution," warns acting Undersecretary of State John Holum.
United States law requires President Clinton, unless overruled by Congress, to end all US military sales and aid, as well as government, private credits, and loans to India.
The US must also oppose all loans and credits to India from multilateral institutions, such as the World Bank, from which New Delhi is the largest borrower. It expects to receive $30 billion from the World Bank before June 30.
Japan, the largest foreign aid donor to India, says it is considering a freeze on loans and other economic sanctions. Japan provided nearly $1 billion in aid this past year. Other countries are taking similar steps, including Germany, which is cancelling $170 million in development aid to India. Further measures may emerge from the summit this Friday of the leaders of the world's seven wealthiest states and Russia in Birmingham, England.
Nuclear weapons: The 'haves' and the 'wanna haves'
* Nations That
Have Nuclear Weapons:
United States France
* Nations Believed to Be
Capable of Building
* Nations Possibly Aspiring
to Develop Nuclear
Iran - The US is concerned
Iran is using its nuclear-
power program to covertly
develop atomic weapons.
North Korea - A 1994
agreement may have frozen
North Korea's alleged effort
to develop nuclear weapons.
* Nations No Longer
Iraq - The International
Atomic Energy Agency says
it cannot find evidence that
Iraq is still developing
Source: Associated Press