U.S. intelligence officials have concluded that the government of Pakistan is secretly building a medium-range missile factory using blueprints and equipment supplied by China, in a development that officials said raises the prospect of a major new U.S. proliferation dispute with Beijing.

The partially completed factory, said by U.S. officials to be located in a suburb of the northern city of Rawalpindi, near Islamabad, is expected to be capable in a year or two of producing most of the major components of a missile modeled after the Chinese-designed M-11. Some officials believe the factory will produce precise duplicates of the missile.

The United States has twice imposed limited economic sanctions against China for selling M-11 missile launchers and finished missile components to Pakistan, but lifted them after China promised to halt such deliveries.

Washington only recently settled a dispute with China over a sale to Pakistan of nuclear-related equipment, and officials say the construction of the missile factory raises the possibility that broad economic sanctions eventually could be imposed on both nations.

The existence of the Pakistani factory has been known to U.S. intelligence officials since last year, when construction evidently began, but it has never been publicly disclosed. Its purpose is described in a recent, classified U.S. National Intelligence Estimate on China's missile-related assistance to Pakistan, which also states that Pakistan may have developed nuclear warheads to be placed atop its M-11 missiles. A National Intelligence Estimate is a consensus view of U.S. intelligence agencies.

U.S. officials said that completion of the factory would for the first time give the Pakistani government an ability to match India's indigenous production of the Prithvi medium-range ballistic missile, which could also be equipped with nuclear warheads. India and Pakistan are archenemies, and Washington fears that any deployment of such weapons could bring the two nations close to the brink of war.

If the U.S. intelligence report about the factory is heeded by U.S. policymakers, the Clinton administration could be forced once again to take up the politically delicate task of confronting China's prickly leadership with an allegation that Beijing is spreading advanced, mass-destruction weaponry to a U.S. ally, according to several officials.

"There is no question there is an involvement" by China in the missile factory, said a U.S. policymaker privy to the intelligence reports. The official cautioned, however, that Washington is seeking additional information about this assistance, and that no formal ruling has been made that China is subject to sanctions under U.S. nonproliferation laws. He called it "a current case" before officials responsible for making such a determination.

A U.S. complaint earlier this year that China sold ring magnets to Pakistan for use in enriching uranium for nuclear arms raised hackles in Beijing and Islamabad and soured China's relations with the United States. The administration eventually decided to avoid a major diplomatic confrontation by agreeing not to impose economic sanctions in exchange for a Chinese pledge that the nuclear sales would not be repeated.

But top administration officials in recent months have been trying to avoid provoking a further confrontation with China. U.S. officials who traveled to Beijing last month for consultations on Chinese policies governing the export of weapons-related goods did not raise the issue of the M-11 factory. According to one official, Washington has complained about it to Pakistan, but the Pakistani leadership denied that such a factory exists.

Four U.S. officials who spoke about the factory on condition they not be named said it appeared to constitute a particularly serious violation of China's repeated pledge to observe the provisions of the Missile Technology Control Regime (MTCR), an agreement among roughly 30 nations that restricts exports of missiles or missile technology capable of carrying nuclear warheads more than 185 miles. The M-11 is assessed at having a range slightly greater than 185 miles when equipped with such warheads.

Under a 1990 law mandating economic sanctions for MTCR violations, the penalty for transferring missile production technology is a cutoff of certain U.S. export licenses and, for communist nations, a ban on most exports to the United States for a period of two years. The sanctions can be waived if the president determines that doing so is required by "national security."

Such sanctions would affect U.S. exports to China of electronics items, military goods and space-related equipment, as well as imports of Chinese-made goods in these categories. The exact value of the goods that might face sanctions is unclear, but in recent years China has exported about $30 billion in goods annually to the United States, while U.S. exporters have shipped about $9 billion a year in goods to China.

U.S. officials said they believe China may have signed a secret contract with Pakistan nearly a decade ago to furnish the missile factory as well as roughly three dozen completed M-11 missiles. According to one official, the intelligence community has been watching "crates of stuff" arrive at the factory from China for months. The contents of some of the crates has been determined with a high degree of certainty, the official said.

While exporting completed missiles is a grave matter, transferring "production technology is the worst," said Leonard S. Spector, an expert on proliferation matters at the Carnegie Endowment for International Peace. "As the old aphorism says: If you give a man a fish, he eats for a day; if you teach a man to fish, he eats for a lifetime. It is a serious offense."

U.S. intelligence analysts are not in total agreement about the facility's capabilities. Some contend that it will be a "turnkey" or "soup to nuts" facility designed and equipped by the Chinese to build complete M-11 replicas, with two missile stages, rocket motors, solid propellant fuel and requisite guidance systems.

Other government analysts said they believe the plant probably will be capable of producing only some of the missiles' components, and that Pakistan may still have to import guidance systems and the specialty steel needed for rocket motor bodies.

Although "there is a spectrum of views" about these details, as one knowledgeable intelligence official said, "there is not much dispute about what this {factory} is. It is a reasonable, analytic judgment" that Chinese and Pakistani technicians are working together there to prepare for the fabrication of medium-range missiles.

Zamir Akram, the deputy chief of mission at the Pakistani Embassy, said in response to a reporter's query that "we have no knowledge of such a factory." Although the city of Rawalpindi harbors a major military base, the suburb where U.S. sources say the factory is being built, Tarwanah, has "no major military or air force facilities. As far as I know, there is nothing of this kind at all," Akram said.

Akram said the U.S. claims evidently originated with "dubious people in so-called intelligence agencies" who seek to malign Pakistan.

An official of the Chinese Embassy here denied that Beijing was helping Pakistan build M-11 missiles. "We consider this matter completely closed," the official said. "There never was any such cooperation. This was discussed when we signed the 1994 agreement" with Washington to bar exports of missiles, such as the M-11, that have an inherent capability to exceed the limit set by the missile control regime.

After the 1994 agreement, Washington lifted sanctions on 10 Chinese companies it claimed had been involved in providing M-11 components to Pakistan.

Several U.S. officials said that although the Clinton administration has so far refused to acknowledge formally that China sold completed M-11 missiles to Pakistan, the National Intelligence Estimate states that it is virtually certain those missiles are in canisters stored at Pakistan's Sargodha Air Force Base, west of Lahore. That is where Pakistan also has maintenance facilities and launchers for the weapons, according to the estimate.

While the estimate was still in draft form, CIA and State Department analysts had bickered over whether the missiles should be declared "operational" because of Pakistan's extensive preparations for launching the weapons on short notice, including training sessions conducted with Chinese assistance.

Some officials expressed concern because the term "operational" might raise undue policy alarms in Washington and upset the Indian government. The dispute was settled by not using the term in the final version of the intelligence report, the officials said. They said the report instead simply states that the missiles can be launched by Pakistan within 48 hours.

After this compromise language was agreed upon, the estimate was approved by Director of Central Intelligence John M. Deutch and circulated to senior policymakers.