After decades of debate, the world is tantalizingly close to achieving a comprehensive nuclear weapons test-ban treaty. So near, and yet so far. One country, India, stands in the way of ratification of the historic agreement. And no amount of arm twisting seems likely to change New Delhi's mind.

Though differences remain over details, last week four of the five big nuclear powers--the U.S., Russia, Britain and France--accepted the text of a test-ban treaty presented to the 61-nation Conference on Disarmament in Geneva. The fifth, China, which conducted its last nuclear test July 29, is still balking, but diplomats expect Beijing to sign. Agreement among the Big Five, however, is not enough to implement the treaty. The U.S., Russia, Britain, France and China insist that the so-called nuclear "threshold" nations--India, Pakistan and Israel--must also initial the pact. Islamabad and Jerusalem have indicated that under the right circumstances they would do so.

That makes India the last holdout. Not only is it adamantly opposed to the proposed treaty, but New Delhi's position has hardened over time. In testimony last week before a congressional committee in Washington, U.S. Secretary of State Warren Christopher offered the hope that once China joins the other nuclear powers in support of the treaty, India might "find a way to come into concurrence as well." But he added that "so far India seems to be determined on its course."

Across the table in Geneva, Indian negotiators offer three objections to the treaty. First, they reject as overly coercive the "entry into force" provision that would ban the testing of atomic weapons by the superpowers and the "threshold" nations. "When nuclear powers say, 'Sign this,' when they compel others to this treaty, that is colonialism," protests K. Subrahmanyam, a strategic-defense expert.

Second, India says signing the treaty would tie its hands in responding to threats from its two unfriendly neighbors, Pakistan and China. As Foreign Minister I.K. Gujral told Parliament last week, "While we have consciously adopted the policy of restraint after demonstrating our [nuclear] capability, we remain fully conscious of the evolving security situation. We are committed to taking all steps necessary to enable us to cope with any threat."

Third, India is upset that the five declared powers would be allowed to keep their nuclear arsenals intact. Taking the high moral ground, New Delhi insists it will not sign a treaty unless it is part of a plan for global nuclear disarmament.

Analysts say India's real objection to the treaty is rooted in domestic politics. All India's major parties oppose the test-ban treaty, as do most of the country's leading newspapers. For the new and somewhat shaky coalition government of Prime Minister H.D. Deve Gowda to push against the tide would be political suicide. Moreover, says Indian columnist Praful Bidwai, "the government's position is fundamentally insincere." Rather than global nuclear disarmament, he fears, what many opponents of the treaty have in their head are "grandiose plans for India to become some kind of superpower."

Domestic politics is also behind American eagerness to close a deal now: President Bill Clinton would like a foreign policy triumph to boost his chances of returning to the White House in November's election. Last month Christopher met with Gujral in Jakarta to argue the case in person. As the U.S. diplomat told Congress, "I urged India strongly not to isolate itself, not to let itself be the barrier to creating this very important international achievement." Christopher came away describing Gujral as "a person of probity and intelligence." But the Foreign Minister had not moved a centimeter. Last week he told Parliament: "We have made it clear that India cannot sign the treaty in its present form. If there are efforts to push forward such a draft, we will have to oppose them."

The treaty supporters' last, desperate hope is to submit the document to the U.N. in September as planned, and then rely on the General Assembly to pressure India to change its position. But at least one New Delhi hard-liner, former army Chief of Staff General V.N. Sharma, insists that the government is immune to such tactics. "If 180 nations sign on the dotted line, it means nothing to India," he declares.

That, say arms-control experts, would be a tragedy. "This is a crucial time," insists Ralph Earle II, deputy director of the U.S. Arms Control and Disarmament Agency. "We have been seeking a test ban for more than 40 years. Now we are so close that it would be a tragedy if the opportunity were lost." Barring a miracle of diplomacy, however, it appears that will happen.

--Reported by Dean Fischer/Washington, Jaime A. FlorCruz/Beijing and Dick Thompson/New Delhi