Indian officials made public today a proposed national nuclear arms doctrine under which only the elected prime minister could authorize a nuclear strike and which would allow India to use such weapons only if attacked by another nuclear power.

The six-page proposal by the National Security Advisory Board, released 15 months after India and regional rival Pakistan staged successive nuclear weapons tests, also recommended that India develop a "triad" strategic defense system in which nuclear weapons could be delivered by land-based missiles, planes and submarines.

The muscular language and unexpected timing of the announcement seemed designed in part to warn Pakistan that a nuclear strike at India would trigger retaliation in kind. While Indian officials emphasized that the statement was not aimed at any specific country, it came after nearly three months of almost constant military clashes between India and Pakistan. Unlike New Delhi, the Islamabad government has not ruled out the first use of nuclear weapons.

The proposal, which has not yet been approved by the 27-member advisory board and would not take effect until a new government is formed after next month's elections, was the Indian government's first formal declaration on the subject of nuclear weapons policy. Previously, officials here had said only that India would forswear first use of nuclear weapons and that its overriding nuclear policy would be to provide a "minimum credible deterrent" to nuclear war, but they had not spelled out what that meant.

"The fundamental purpose of Indian nuclear weapons is to deter the use and threat of use of nuclear weapons by a state or entity against India and its forces," the document said. "Any adversary must know that India can and will retaliate with sufficient nuclear weapons to inflict destruction and punishment . . . if nuclear weapons are used against India and its forces."

The United States, which has been engaged in high-level talks with both India and Pakistan in hopes of preventing a nuclear arms race in South Asia, reacted coolly to today's announcement. State Department spokesman James P. Rubin said the United States was not consulted on the document and continues to believe that "possession of nuclear weapons in this form or similar forms doesn't enhance" the security of India and Pakistan.

"We think it would be unwise to move in the direction of developing a nuclear deterrent and encouraging thereby the other country to develop a nuclear deterrent and thereby creating an action-reaction cycle that will increase the risks to both countries," Rubin said in Washington.

Joseph Cirincione, director of the Nonproliferation Project at the Carnegie Endowment for International Peace, said the Indian announcement was part of a "slow, steady movement toward eventual deployment of nuclear weapons in South Asia. That is what is dangerous and what the United States has tried unsuccessfully to stop."

Anti-nuclear activists here described the proposal as containing several new and alarming elements that could provoke a strong reaction from both Pakistan and China, India's other nuclear-armed neighbor. India cited China as its principal concern when it staged its nuclear tests in May 1998, while Pakistan is a perennial rival with which India has fought three wars in 52 years.

The proposal asserts that India would respond to a nuclear attack "with punitive retaliation should deterrence fail." This, said Praful Bidwai, head of India's leading anti-nuclear organization, adds a disturbing new element to the country's stance on nuclear weapons. "Last year, our government presented its doctrine in the garb of restraint and responsibility; now they are disclosing the nasty side of no first use," Bidwai said. "The language is menacing. I think it will be seen by people in Pakistan, especially the military hawks, as a provocation, and that's how nuclear races are ignited."

But Brajesh Mishra, the government's national security adviser, insisted that India intends to develop a cautious, carefully controlled nuclear policy. Mishra and another member of the National Security Advisory Board, defense expert K. Subhramanyam, made the document public at a news conference.

"The cardinal principle is that of civilian control," Mishra said. India's systematic, carefully orchestrated defeat of Pakistani-based guerrillas during a prolonged border clash in Kashmir last month, he said, "showed that we behaved with restraint and responsibility" in a conventional conflict. "That will also guide our actions in the use of nuclear weapons."

The draft doctrine also proposes that India create a "robust" command and control system in which only the prime minister, or someone designated by him, can authorize the use of nuclear weapons. It did not address the role of the military in the handling and deployment of nuclear warheads, saying only that the "actual size, components, deployment and employment of nuclear forces will be decided" based on strategic, technological and security considerations.

Exactly how India or Pakistan might stage a nuclear strike is still largely a matter of speculation. It is possible that both countries already are capable of dropping a nuclear bomb from an airplane; both countries also have tested missiles capable of carrying nuclear warheads.

Michael Krepon, president of the Henry L. Stimson Center, a Washington-based research organization, said the document failed to say whether India would keep its missiles launch-ready and whether such missiles will be fitted with warheads. "Based on this document, it will be hard for other countries to believe in India's assurance of no first use," Krepon said. "To other countries it will look like readiness to use."

But the Carnegie Endowment's Cirincione said nevertheless that the draft document appears to be an attempt to reassure the world that India has a responsible, thought out nuclear arms policy and a clear command structure. "This says the weapons are not something that regional commanders will have unrestricted access to, which is a concern in a country with a history of poor communications between troops in the field and headquarters," Cirincione said.

It was not clear what impact the proposed policy, if adopted, would have on India's stance on the Comprehensive Test Ban Treaty, which the United States has been pressing it to sign for months. Mishra said that would be decided by the next government and was not discussed by the panel.

Staff writer Douglas Farah in Washington contributed to this report.