In January 2006, an Indian government agency purchased newspaper ads seeking help in building an obscure piece of metal machinery. The details of the project, available to bidders, were laid out in a series of drawings that jolted nuclear weapons experts who discovered them that spring.

The blueprints depicted the inner workings of a centrifuge, a machine used to enrich uranium for nuclear bombs. In most Western countries, such drawings would be considered secret, but the Indian diagrams were available for a nominal bidding fee, said David Albright, a former U.N. weapons inspector. He said he acquired the drawings to prove a point.

"We got them for about $10," said Albright, who called the incident a "serious leak of sensitive nuclear information."

India has since tightened its bidding procedures, but the incident has fueled concerns among opponents of a U.S.-Indian civilian nuclear deal that Congress is expected to consider in the coming weeks.

The accord, first announced in 2005 by the Bush administration, would lift a decades-old moratorium on nuclear trade with India, allowing U.S. companies to share sensitive technology despite that country's refusal to ban nuclear testing or sign the nuclear Non-Proliferation Treaty. Backers of the deal say it will cement U.S. ties with India and reward a country that has been a responsible steward of nuclear technology since it first joined the nuclear weapons club in 1974.

But opponents say India's record on nonproliferation is not as unblemished as is claimed by the White House, which regards the nuclear pact as one of the foreign-policy highlights of the Bush administration's second term. Critics, including former U.S. diplomats, military officers and arms-control officials, accuse the White House of rushing the agreement through Congress without considering the long-term implications.

"This deal significantly weakens U.S. and international security," said retired Army Lt. Gen. Robert G. Gard Jr., chairman of the Washington-based Center for Arms Control and Non-Proliferation. Yesterday, a group of 34 arms-control advocates and former government officials urged Congress to reject the deal in its current form.

Administration officials have repeatedly lauded India's efforts to prevent the spread of nuclear technology, contrasting its behavior with that of Pakistan, the home base of Abdul Qadeer Khan, the acknowledged nuclear smuggler who delivered weapons secrets to Libya, Iran and North Korea.

R. Nicholas Burns, the former undersecretary of state for political affairs and a chief supporter of the landmark accord, said in a recent forum that India was "playing by the rules of the [nuclear] club but not allowed to join the club." Burns said the agreement "strengthened the international nonproliferation regime because it resolves an inherent contradiction in the regime."

Likewise, India's government says it deserves the trust of the world's nuclear gatekeepers. "India has an impeccable nonproliferation record," External Affairs Minister Pranab Mukherjee said last week. "We have in place an effective and comprehensive system of national export controls."

Opponents point to what they call decades of deceptive practices India has used to acquire nuclear materials from foreign governments. A draft report by Albright and his Institute for Science and International Security, a Washington-based nonprofit that monitors the spread of weapons technology, cites recent incidents in which it says India engaged in "illicit nuclear trade."

In an instance alleged by ISIS, India used an array of trading companies to secretly acquire tons of tributyl phosphate, a chemical used to separate plutonium from spent nuclear fuel. China, a longtime supplier of TBP to India, halted shipments of the chemical in 2003 after U.S. criticism. India turned to independent trading firms that acquired TBP from German and Russian companies without revealing the true destination, the report said.

The ISIS report, due for release today, included photocopies of some of the centrifuge drawings obtained by Albright, although the group removed key specifications. Albright said he shared his findings with State Department officials but was turned away.

"It didn't fit with their talking points," Albright said. "At the highest level, they were dismissive of our concerns."

A State Department spokesman declined to comment on Albright's report, saying it had not been reviewed, and said the agreement was in the U.S. interest.

Other opponents have cited transfers of sensitive weapons technology by individual Indian scientists. In 2004, the State Department slapped sanctions on two Indian nuclear scientists alleged to have passed heavy-water technology to Iran. At least four Indian companies have been sanctioned over sales of missile technology to Tehran.

Such incidents underscore concerns about the possible transfer of India's expanded nuclear know-how by rogue scientists and businessmen, said Henry Sokolski, the Defense Department's top nonproliferation official in the George H.W. Bush administration.

As trade grows between India and Iran, so does the risk of "transfers of technology that could be useful for Iran's purported weapons of mass destruction," Sokolski said.

© 2008 The Washington Post Company