Federal prosecutors in the Joseph P. Yeldell-Dominic F. Antoneli Jr. bribery case balked yesterday at disclosing grand jury testimony of all the witnesses in the case, saying some may be "pressured" when details of their cooperation are revealed.

Assistant U.S. Attorneys Richard L. Beizer and Henry F. Schuelke said they would provide defense attorneys the grand jury material involving about 40 government witnesses, but not the remaining 12 or so.

"The government does so because, by disclosure at this time, these witnesses, due to their employment by the District of Columbia government or by an institution on whose board of directors one of the defendants serves, or otherwise, may feel themselves subject for an inordinate period of time to unwarranted pressures in their work and social relationships," the prosecutors said.

Yeldell, who is on leave from his job as a top District mayoral aide, and Antoneli, a multimillionaire parking lot owner and developor, are charged with bribery in connection with the allegedly corrupt awarding of a city lease.

Yeldell is accused of helping arrange a city lease on a building owned by Antonelli in exchange for a $33,000 hidden loan at favorable rates. The government leased the building for $5.6 million after Antonelli had purchased it and other property for $800,000.

Both men have pleaded innocent to the charges of bribery and a conspiracy charge alleging that District citizens were deprived of Yeldell's proper use of his office.

The issue of pretrial disclosure of witnesses' testimony arose when the two men were arranged before U.S. District Judge Gerhard A. Gesell. Gesell urged the government to provide informal pretrial "discovery" of grand jury matters - not actually required until after each witness testifies at trial - to attorneys for Yeldell and Antonelli.

Beizer agreed at the time that in most instances such materials would be made available, but said he would reports to Gesell later about any problems that might arise.

Yesterday's letter from prosecutors to Gesell, filed publicly by the judge, apparently was the result of concerns raised by certain witnesses about pressure that might be placed on them once the defendants or associates became ware of their specific testimony.

Although the testimony will come out at the trial, the prosecutors apparently felt it was unnecessary to expose the 12 or so selected witnesses to pressure any sooner than necessary.

The material will be made available "shortly before trial." prosectuors Schuelke and Beizer said in the letter to Gesell.