WASHINGTON (AP) _ A declassified memo shows U.S. military intelligence knew as early as the first Reagan administration that China was stealing U.S. nuclear secrets to improve its arsenal.

An analyst said Wednesday he doubts that the 1984 memo ever reached President Reagan's National Security Council inside the White House, but that the information it contained ``certainly'' would have been known to key officials inside the government.

``Increased access to this technology and continued Chinese efforts will in the 1980s and early 1990s show up as qualitative warhead improvements,'' the Defense Intelligence Agency said in the document, known as an ``estimative brief.''

``Qualitative improvements that the Chinese are developing for their nuclear warheads will depend on the benefits that Chinese are now deriving from both overt contact with U.S. scientists and technology and the covert acquisition of U.S. technology,'' the document added.

A private group in Washington, the National Security Archive, used the Freedom of Information Act to obtain the four-page document, entitled ``Nuclear Weapons Systems in China,'' from the DIA, a Pentagon agency engaged in intelligence analysis.

``I think the document says people at DIA and I presume others in the intelligence community understood exactly how the Chinese were going to go about improving their arsenal,'' said Jeffrey Richelson, who is compiling a 15,000-page collection of declassified documents on U.S.-Chinese relations.

Richelson said he doubts that the DIA memo was forwarded to President Reagan's National Security Council. ``Certainly key officials in the government would understand the essence of the observation about how the Chinese would go about improving their nuclear arsenal,'' he said.

``There is evidence that the Chinese have been successful in assimilating into their nuclear weapons program United States technology,'' states the April 24, 1984 assessment. ``In some areas, the gap between United States and Chinese nuclear warhead technology may begin to narrow.''

The agency predicted that China would improve its nuclear program in terms of ``increased warhead reliability and confidence, development of more compact warheads, especially for tactical nuclear applications and possibly for MRV warheads, increased hardening of warheads in a nuclear antiballistic missile environment, tailored output devices, such as enhanced radiation and improved warhead safety, storage and logistics procedures.''

Documents such as the DIA estimate are supplying ammunition to Democrats eager to move the blame for China's theft of U.S. nuclear secrets away from the Clinton administration and onto the Reagan and Bush administrations.

In the aftermath of the release of the Cox report, Democrats on Capitol Hill circulated a document entitled ``What President Bush knew,'' a five-page summary of dire warnings about Chinese espionage and security lapses at U.S. nuclear laboratories going back to 1980.

The summary juxtaposed Texas Gov. George W. Bush's strong criticism of Clinton with a lengthy recitation of incidents from the 1980s and early 1990s about Chinese nuclear espionage.

Bush said ``there is only one administration that has been given the news'' about Chinese espionage at weapons labs ``and that's the Clinton administration. The interesting question is when did they know?''

The Democrats' summary pointed to:

_Newspaper reports when Bush's father was president that Chinese intelligence agents had stolen nuclear weapons secrets from the Lawrence Livermore National Laboratory.

_A lengthy series of General Accounting Office reports detailing security problems at the weapons labs that made them vulnerable to espionage.

The Democrats' summary also highlighted a recent published comment by Bush administration national security adviser Brent Scowcroft that lab security was not an issue during his time in office. ''If allegations of Chinese spying had been widely known, they would have been a major issue in the Clinton-Gore campaign in 1992,'' responded Karen Hughes, a spokeswoman for Gov. Bush. ``They were not'' an issue ``because it's not true'' that the allegations were widely known.

``America deserves leaders who are honest, not partisans who attempt to spin their way out of responsibility for a major embarrassment that happened on their watch,'' said Hughes.