A nuclear agreement that was to have been emblematic of new strategic relations between the United Stares and India appears to be falling apart, with serious consequence all around.

For President George Bush, the faltering of the civilian nuclear agreement will be only a moderate diplomatic setback, overshadowed as it is by the war in Iraq and Afghanistan, the hostility of Iran and the Israeli-Arab conflict. Even so, the failure will rob Bush of what might have been a modest triumph in the final months of his presidency.

For India, the consequences are likely to be more severe. The political life of Prime Minister Manmohan Singh's government is in jeopardy. India's international standing, including its aspiration to become a permanent member of the United Nations Security Council, will suffer. India's economic growth, which has started to rival China's, will be slowed by shortages of energy.

India's swirling political infighting seems to be the fundamental cause for the breakup of the nuclear agreement. The leftist parties, which are part of the ruling coalition under Prime Minister Singh, have opposed the agreement as diluting India's sovereignty. That is often a powerful argument in former British and other colonies jealous of their independence.

In this instance, the left has made common cause with rightist and nationalist parties who are intent on bringing down the Singh government, which has been in office since May 2004. Singh, an economist by profession who has instituted several reforms, had pushed the nuclear agreement despite opposition within his own government.

Of this about-face, Prem Shankar Jha, a prominent Indian commentator in Delhi, wrote: "The damage that not having the courage to complete this deal will do to India is almost beyond comprehension." He asserted this week: "Reneging now will make India a permanent outcast" and contended "India's behavior shows that it never intended to be a constructive partner in the management of the world."

The nuclear agreement, which has been more than two years in the making, would have given India access to fresh supplies of nuclear fuel and technology. It would have brought India's nuclear energy program under the International Atomic Energy Agency's safety inspections. India would have pledged that its civilian nuclear program would be dedicated to peaceful uses.

The agreement, however, would not have halted India's effort to expand its arsenal of nuclear weapons nor to stop the transfer of its current supply of nuclear materials from civilian to weapons programs. Critics of the agreement in India, the U.S., and elsewhere insisted that it would weaken the international effort to prevent the spread of nuclear arms.

Bush and Singh promoted the nuclear agreement into the centerpiece of what Nicholas Burns, the under secretary of state for political affairs, called in 2005 "a broad, global partnership of the likes that we've not seen with India since India's founding in 1947."

In a speech in Delhi in March 2006, Bush noted that the U.S. and India had been kept apart during the Cold War "by the rivalries that divided the world." India was a leader in the Non-Aligned Movement and drew much of its military assistance from the Soviet Union.

In contrast, the president said, "India in the 21st century is a natural partner of the United States." He pointed to the democracies in both trade and investment between the two, and military cooperation such as the Indian Navy's guarding the Strait of Malacca, the sea-lane between Singapore and Indonesia that is vital to international trade.

The president further noted India's economic expansion required more electricity. "And the cleanest and most reliable way to meet that need," the president said, "is through civilian nuclear power." He asserted that nuclear power would help cut pollution in India, which generates more than half of its electricity by burning soft coal that pollutes the air.

The president repeated many of these points last December when he signed the legislation that Congress passed with strong bipartisan support to authorize the U.S. to provide nuclear help to India. With that, the U.S. had completed its part of the deal and needed only a go-ahead from India to implement it.

Against this American backdrop, Prem Shankar Jha said India's retreat from the agreement bordered on disaster. "It may not be the end of the world," he wrote, "but it will be a very long time before we are invited to the High Table again."

Richard Halloran is a Honolulu-based journalist and former New York Times correspondent in Asia. His column appears weekly in Sunday's Focus section.