U.S. intelligence agencies have determined that China is helping Algeria construct a nuclear reactor that may eventually produce fuel for nuclear weapons, a move that may violate past Chinese pledges on nuclear transfers, according to knowledgeable government officials.

The disclosure, which closely follows reports of Chinese efforts to export ballistic missiles to Pakistan and Syria, has evoked protests on Capitol Hill and may undermine a Bush administration plan to renew favorable economic terms for Chinese trade, the officials said.

China pledged publicly in 1984 that the only nuclear technology it would export would be technology subject to international safeguards against nuclear weapons proliferation. Such safeguards include inspection by officials of the International Atomic Energy Agency (IAEA). But none of China's assistance to Algeria has been inspected, officials said.

Both China and Algeria have denied any collaboration on nuclear weapons. But U.S. intelligence experts say they believe the reactor, which is several years from completion, is larger than would be required solely for routine nuclear research. The experts also say that the construction site for the Algerian reactor shows no provision for the generation or use of any electrical power from the facility.

U.S. suspicions about the facility have been heightened by the apparent presence of a Soviet-made, antiaircraft battery near the remote site located close to Algeria's Mediterranean coastline, several officials said.

One official said the Bush administration has recently protested to both countries about the nuclear technology transfer, but said he did not know what the responses were. A State Department spokesman said last week that Washington was aware of the Chinese assistance to Algeria, but had no reason to conclude that Beijing's assistance was knowingly part of a nuclear weapons development effort.

An official at the Algerian Embassy in Washington said the aim of the cooperation was "exclusively peaceful." He said Algeria supported international constraints on nuclear proliferation, but did not know his government's position on IAEA inspections of the facility.

A spokesman at the Chinese Embassy said his government "does not . . . help other countries develop nuclear weapons." He said Chinese cooperation in Algerian research on nuclear technology was "solely for peaceful purposes," but also could not say if it would eventually be subject to IAEA inspection.

But Senate Foreign Relations subcommittee chairman Joseph R. Biden Jr. (D-Del.), citing earlier news reports about the Algerian program and possible Chinese missile sales to Pakistan and Syria, said this week that "it appears China is rapidly becoming a rogue elephant among the community of nations."

Biden said he believes the United States repeatedly has been misled by Chinese Foreign Ministry assurances that Beijing would not transfer technology for such weapons of mass destruction as missiles or nuclear bombs. If China's behavior continues, he said, "we should be prepared to retaliate with a clear and unequivocal message that they will understand -- that is, denying China 'most favored nation' trade status."

The trade certification, which must be sought annually in an administration statement to Congress by June 30, enables Chinese producers to save hundreds of millions of dollars by paying low tariffs on goods exported to the United States. The House last year voted to withdraw the certification due to concerns over Chinese suppression of internal dissent, but the Senate voted to uphold the renewal after extensive lobbying by Bush.

A key Senate aide said, "There is now a strong bipartisan consensus that countries who participate in proliferation of these weapons are in trouble," and many Republican legislators may defect from the administration's position on Chinese trade this year.

Several independent experts on Chinese arms exports, writing in the current issue of the journal International Security, forecast that China will not accept significant constraints on its exports of such sophisticated military equipment because Beijing leaders believe "the sales translate into hard cash for modernization, enhanced domestic power and greater international influence."

Most of the weapons exports are arranged directly by Chinese corporations controlled by autonomous units of the military and staffed by family-based clans or offspring of powerful Chinese leaders, making them highly resistant to outside political pressures or Western criticism, wrote John W. Lewis, Hua Di and Xue Litai of Stanford University.

U.S. policy-makers such as former defense secretary Frank C. Carlucci have been misled by assurances from senior officials of the Chinese Foreign Ministry that such exports would not occur, the scholars wrote, when in fact these officials "did not make policy in the arena of national security or arms sales," and spoke only for their ministry instead of the government at large.