Two eminent nuclear scientists, both of whom directed national nuclear laboratories when key U.S. warheads were developed, say information allegedly stolen by China through espionage was not as valuable as portrayed by a House select committee that published a report on security lapses last week.

The two are Harold M. Agnew, who directed what was called the Los Alamos Scientific Laboratory from 1970 to 1979, when the W-88 warhead for the Trident submarine-launched missile was developed; and Johnny S. Foster, who directed the Lawrence Livermore National Laboratory from 1952 through 1965, developing the first miniaturized nuclear weapons as well as the so-called neutron warhead, the W-70. They said data on U.S. nuclear warheads that the committee concluded were obtained through Chinese espionage only added to what China's scientists already knew: that powerful, miniaturized nuclear weapons could be built.

The House Select Committee on U.S. National Security and Military/Commercial Concerns with the People's Republic of China, chaired by Rep. Christopher Cox (R-Calif.), concluded that the "design information" on this nation's "most advanced thermonuclear weapons" enabled Beijing "to design, develop, and successfully test modern strategic nuclear weapons sooner than would otherwise have been possible." The panel also concluded "stolen U.S. nuclear secrets" gave China "design information on thermonuclear weapons on a par with our own" and that without that information "it would have been virtually impossible for the [Chinese] to fabricate and test successfully small nuclear warheads prior to its 1996 pledge to adhere to the Comprehensive Test Ban Treaty."

Since the report's release, some experts and Democratic members of Congress have suggested the panel in some instances extrapolated worst-case conclusions from findings that could have been interpreted less alarmingly. Former intelligence officials also have found significance in the fact that a Chinese document showing knowledge of U.S. W-88 warhead design -- one of the committee's main findings -- came from what the CIA believes was a double agent.

The panel cited the W-88 and the W-70 as warheads whose designs were obtained by China. But Agnew and Foster said even data on the size, weight, shape and yield, although highly classified, do not represent a warhead's design in any real sense.

"We showed them what's possible," Foster said in a telephone interview, "and they probably learned that some time ago when the size and shape of the reentry vehicle [which carries the nuclear warhead] and its [explosive] yield [were first made] public."

Foster, who left Livermore in 1965 to head research and development at the Defense Department during the Johnson administration and part of the Nixon administration, later chaired the Defense Science Board while George Bush was president. He also was on a panel created by CIA Director George J. Tenet to review intelligence agencies' analysis of China's alleged espionage on U.S. labs.

Foster said the Chinese have shown "they are smart" when it comes to nuclear designs, but the tricks in "fabrication of the [nuclear material] metals" involved in these sophisticated warheads and the "purity of the plutonium available" are much more difficult to accomplish. Foster helped develop the W-87, the warhead for the MX intercontinental ballistic missile that was the first time U.S. scientists almost doubled the yield of a device using the same amount of nuclear material.

Agnew, who worked on the first atomic bomb that was dropped and filmed it exploding over Hiroshima from a chase plane, said the original W-88 design went back to the 1950s and was a "delicate and neat package" put together to compete with Foster's W-87. But, Agnew added, "The difficulty is actually making them." Agnew, 78, has remained active since leaving Los Alamos, as an officer of General Atomic Corp. and as a consultant on nuclear matters to several administrations.

Agnew said he and others at Los Alamos were aware that China, like other countries, was attempting to gather information about U.S. nuclear programs. He was among the first U.S. nuclear scientists invited to visit China but stopped going because of his hosts' repeated questions about weapons.

But, he said, "The Chinese physicists certainly have the brains to develop their own weapons. . . . They are smart and have been trained in England, Scotland and the U.S."

Agnew said that much of the information alleged to have been stolen by China was made public decades ago, although still considered classified within government. He said he attended a public lecture a year ago given by the Natural Resources Defense Council, which first published its U.S. Nuclear Forces and Capabilities handbook in 1984. The speaker was so detailed with what was still considered classified, Agnew told him it "would be appropriate for all new hires at Los Alamos."

Two other former lab directors criticized a Cox panel conclusion that any new Chinese thermonuclear warhead would contain elements of the W-70 and W-88. The concept was given the committee by Notra Trulock, at the time head of intelligence for the Energy Department.

Because the former directors have had to deal with Congress on their budgets, they all respect the fact that legislators "are trained to simplify," as one put it. In this case, however, "politicians with little knowledge have had a knee-jerk reaction on what should be done," the former director said.

This former director called talk about barring Chinese and other foreign scientists from the labs "a punishment that doesn't fit the crime." He said that if there is a traitor in a lab, preventing foreigners from visiting "will have no effect at all."

Neither Agnew nor Foster was asked to appear before the Cox committee. Panel member John M. Spratt Jr. (D-S.C.), who has followed nuclear weapons matters for years on the Armed Services Committee, said last week that he regretted not having suggested calling "some of the senior statesmen of the nuclear labs."

"We were moving at a fast clip," Spratt said, noting that the first information given Cox panel members alleging Chinese espionage at the labs came on Oct. 21, and the panel had agreed to conclude taking testimony by Nov. 15 to have time to draft a report due Jan. 3. He said the panel heard analysis of the nuclear weapons losses and their meanings from Trulock, a CIA analyst and a Los Alamos employee who was not a bomb builder.

The three current lab directors testified, but only on the foreign visitors program, and before Trulock disclosed his views of Chinese espionage.