The State Department was so preoccupied with bureaucratic niceties and legalistic constraints that it was virtually blind to warnings of imminent danger at Jonestown last year, according to a study commissioned by Secretary of State Cyrus R. Vance.

The study found that some of the most prized diplomatic attributes - caution, circumspection and tact - ultimately emasculated what few efforts were made to intervene at the Peoples Temple commune in Guyana before the murders and mass suicide there last November.

"The single most important substantive failure," the report said, occurred last June, five months before the Jonestown tragedy. After receiving repeated allegations concerning concentration camp-type conditions and mass suicide threats at Jonestown, the U.S. ambassador in Guyana cabled Washington June 6 for authorization to seek Guyanese intervention.

But the cable was so cautious and so couched in legalese that "its intended import was obscured." The request was rejected with a "simplistic reply" from Washington, the report said.

A month earlier, the report continued, the State Department "all but ignored" a petition from a Peoples Temple defector, Timothy Stoen, in which he, too, spoke of possible mass suicide. "I wish there were some way to convince you that the situation in Jonestown is desperate," Stoen wrote. There exists "a threat so chilling as to be incomprehensible to the average decent person."

Last Nov. 18, Peoples Temple members murdered visiting Rep. Leo Ryan (D-Calif.) and four others accompanying him on a Jonestown inspection. More than 900 Temple followers then died - most by comsuming a cyanide poison mixture administered at the orders of the Rev. Jim Jones, the Temple leader.

The State Department study was prepared by two retired senior Foreign Service officers, John Hugh Crimmins and Stanley S. Carpenter. Because of the department's failure, they recommended that department "undertake urgently a thorough high-level review" of the government's abilities to cope with problems Americans may have abroad.

The report tracks State Department handling of Jonestown from the time emigration first began, largely from California, to the day of the tragedy. During the year preceding the killings, the State Department and the U.S. embassy in Guyana had been showered with complaints from Peoples Temple members and relatives about conditions at Jonestown, on the one hand, and equally strenuous charges on the other hand, by Temple leaders and Temple lawyer Mark Lane of harassment directed at the Temple.

By May 1978, officials had heard unverified reports of people held in bondage, arms smuggling into Jonestown, threats of mass suicide, a drugged appearance of Jonestown residents and the mental instability of Jones himself.

Numerous "contraints" then seemed to take over and limit the department's flexibility, the report said. Among them:

Consular officials inGuyana wanted to tread cautiously because they were dealing with two competing groups of American citizens, each of which had enlisted prominent people, including public officials, in their cause. The Peoples Temple also had high-level friends in the Guyana government.

Attempts to verify the complaints were hampered by the perceived need, under the U.S. Privacy Act, to notify Jones in advance of inspection trips and of the names of Jonestown residents to be interviewed.

Restrictions on U.S. surveillance of Americans overseas prevented the use of standard intelligence-gathering methods to try to find out what was happening in Jonestown.

The Freedom of Information Act, which often allows public inspection of confidential government documents, induced officials to be circumspect in their cables and memos, for fear that parties to the Jonestown dispute might someday see them. The same apprehension, the report says, caused officials to ignore nuance and downplay any information they could not absolutely verify for fear they would be accused of taking sides.

The report said that this inclination was most damaging in the handling by Ambassador John Burke of his June 1978 cable to Washington seeking permission to approach the Guyanese government.

"In drafting the telegram, the ambassador consciously put the issues in legal terms, using as careful and judicious language as he could. Assuming that the telegram would get into the hands of Peoples Temple in one way or another and having specifically in mind the Freedom of Information Act, the ambassador prepared the telegram with the purpose of having it stand absolutely by itself."

When the June cable arrived in Washington, the report said, nobody really understood it. It was routinely sent - without any special classification of urgency - and routinely rejected. It never got to the higher levels of the department - the assistant secretary level, a failure that the report found common throughout the period.

The same theme - overcautiousness - dominated handling of the matter at almost all levels. Officials either didn't trust their own instincts or felt constrained in reporting them up the ladder, even when they had deep suspicions, the study found.

While inspection tours of Jonestown could not vertify the complaints, U.S. officials often doubted that they were seeing the truth on their visits. The doubts were generally discounted as unverifiable.

One desk officer visiting Jonestown, for example, "was struck by the feeling that many of the persons with whom he met and spoke appeared drugged or robot-like in their reactions," the report said.But "nothing his short stay - four hours - and his lack of training in what would amount to a psychiatric skill, he qualified the statement by saying it was a personal reaction probably influenced by reading about religious brainwashing."

A similar pattern occurred when Deborah Blakey, a defector, first revealed the mass-suicide threats to U.S. officials.The report said that "even though her charges were not accepted at face value and doubts about her motives lingered, there was present in the embassy the thought: what if she is telling the truth?"