The Chinese government's case against a New York Times researcher who has been held on suspicion of revealing state secrets for more than a year relies almost entirely on a copy of an internal Times memo obtained by the State Security Ministry, according to a confidential ministry document urging prosecutors to indict the researcher.

State security agents obtained a copy of the memo as part of an investigation to uncover the source of a Times article predicting the retirement of China's former president, people familiar with the probe said. But it is unclear how the agents gained access to the memo, which was written by the researcher, Zhao Yan, and describes a possible leadership dispute over military promotions.

The document requesting Zhao's indictment includes a copy of the memo in an inventory of evidence collected in the case.

Susan Chira, the Times' foreign editor, said the newspaper did not give the government a copy of the memo, which was stored in a file cabinet in the Times Beijing bureau. Asked to comment on the possibility that state security agents searched the office and photocopied it, she replied: "If that were true, we'd be upset. . . . We really don't know what happened. Obviously, they got hold of it."

A surreptitious search of the Times bureau by state security agents, or by employees of the Times obeying their instructions, could violate Chinese law.

Zhao was detained Sept. 17, 2004, in the party's attempt to uncover the source of a Times article 10 days earlier predicting the former president's retirement, and the researcher's memo is the only significant piece of evidence against him, according to the State Security document, which authorities made available to the Times and to Zhao's family.

But the memo, which was examined by The Washington Post, contains no information about former president Jiang Zemin's decision to resign as chief of the nation's military. Instead, in the memo -- four sentences scrawled in blue ink on a scrap of white paper -- Zhao described only a possible dispute between Jiang and his successor, President Hu Jintao, over promotions for two top army generals.

The failure to uncover the source of the Times report, and the weak case that state security agents have built against Zhao, could embarrass Hu, who approved the investigation and has continued to issue instructions concerning it, according to people familiar with the probe, including a party official.

Prosecutors in Beijing have twice declined to indict Zhao, first in early July and again last week. Under Chinese law, state security agents have one more month to gather evidence. After reviewing any new material, prosecutors will then be forced to make a final decision about whether to indict or release Zhao.

Given Hu's involvement, legal analysts said, prosecutors are most likely awaiting further instructions from party superiors about how to proceed.

Both Zhao and the Times have denied that he revealed any state secrets or provided any information about Jiang's retirement to the newspaper. If convicted, he could be the first journalist employed by an American news organization to be imprisoned by the Chinese government in decades.

Secretary of State Condoleezza Rice has raised Zhao's detention with the Chinese foreign minister, and his name was on a short list of prisoners that a U.S. official gave the Chinese during a meeting last month between President Bush and Hu at the United Nations.

Since taking office three years ago, Hu has presided over a clampdown on dissent that has resulted in the arrest of several journalists and writers. But the Zhao case is unusual because Hu almost certainly will personally determine how it is resolved, analysts said.

The National Administration for the Protection of State Secrets, the agency responsible for classifying information in China, has already certified the contents of Zhao's memo as "top secret," the highest classification, according to the document urging Zhao's indictment. People convicted of disclosing such secrets face a minimum 10-year prison sentence and, in severe cases, can be sentenced to death.

Legal scholars say China's state secrets law is so vague that almost all information can be deemed a secret, even rumors that are untrue.

Zhao's memo, written in July 2004, said that Hu proposed promoting two generals to serve as vice chairmen of the Central Military Commission, the nation's top military body, and that Jiang rejected the plan. But weeks later, one of the generals, Xu Caihou, was in fact promoted, casting doubt on Zhao's account.

Mo Shaoping, the lawyer hired by the Times to defend Zhao, said his client was just speculating when he wrote the memo. In any case, he argued, "changes in government leaders, including military leaders, aren't state secrets. It's something that citizens have a right to know about."

Joseph Kahn, the Beijing bureau chief of the Times, said he regarded Zhao's information as "interesting, unconfirmed speculation." He mentioned it at the bottom of the article predicting Jiang's retirement, in a section about possible jockeying between Hu and Jiang.

People familiar with the probe said state security agents obtained a copy of Zhao's memo in the nine days after the publication of the Times report and before Zhao's arrest. Kahn said he had no reason to believe any Times employees helped the agents, noting that he and Zhao were the only people in the office who knew the memo existed.

If state security agents searched the office or recruited an employee of the Times to search it, they would have been required under Chinese law to do so in the presence of a representative of the newspaper and then provide a receipt for any items taken, said Jerome Cohen, a scholar of Chinese law who has been retained by the Times to assist with Zhao's defense.

A party official who spoke on condition of anonymity said state security agents were under pressure to identify the source of the Times report and may have arrested Zhao in the hope he could be intimidated into providing a name or, if he refused to cooperate, blamed for the leak himself. But Kahn said Zhao does not know the source of the article.

Zhao, 43, developed a reputation as an aggressive journalist writing about corruption and rural poverty for various Chinese publications over the past decade, but he sometimes crossed the line into activism by providing legal advice to farmers and others with grievances against the government, friends and colleagues said.

As a result, they said, state security agents placed him under surveillance and began visiting him regularly even before he joined the Times in April 2004. Colleagues said Zhao left his prior job, with China Reform magazine, after some editors there accused him of accepting money from the subjects of his stories, a standard practice in the Chinese news media.

In a possible attempt to pressure him, state security agents added another charge against Zhao in April, alleging that he committed fraud in 2001 by accepting a payment from a farmer trying to avoid a sentence to a labor camp. Mo, the lawyer, said that Zhao has denied the charge and that a witness has come forward in his defense. The Times also defended him.

"It's hard to understand why he is now being charged with something that is years old," said Chira, the Times' foreign editor. "In any case, we believe this man is wrongfully in jail and needs to be released because he has done nothing wrong."