Naval Investigative Service headquarters ordered two field agents to change from "nondeceptive" to "deceptive" their evaluations of Marine Cpl. Arnold Bracy's reponses to polygraph questions about espionage at the U.S. Embassy in Moscow, officials said yesterday.

The disclosure appeared to strike another blow at the military's troubled investigation and prosecution of the first-ever espionage allegations involving the elite unit assigned to guard the most sensitive U.S. diplomatic installation.

The officials, who spoke on condition that they not be identified, said the action was ordered by NIS headquarters in March to correct an "administrative error" by the two San Diego-based NIS agents who interrogated Bracy, one of two former Marine security guards now facing espionage charges.

The officials said the two agents had failed to follow longstanding Defense Department instructions on analyzing polygraph results. They said public disclosure of

the fact that the investigators'

ranking of Bracy's responses had been countermanded should have no impact on prosecution of the case.

But Bracy's attorneys called the development "most significant" and said that when Bracy's pretrial military hearing resumes Tuesday they would seek to question under oath the senior Navy officials involved in the decision.

"This shows the lengths to which they have gone since the beginning to find something on Cpl. Bracy, whether it is there or not," said Charles Carter, the Baltimore-based NAACP lawyer representing the 21-year-old Marine.