U.S. Attorney Jay B. Stephens said in court papers filed yesterday that D.C. Mayor Marion Barry does not deserve a new trial on his misdemeanor cocaine possession conviction because he has failed to prove that an unrelated drug sting witnessed by jurors in the case tainted their verdict.

The sting in question occurred last summer at a New Carrollton hotel where the Barry jury was being sequestered. Conducted by the Drug Enforcement Administration, the FBI and Prince George's County police, it was aimed at drug suspect Brian Lee Tribble, acquitted in 1987 of supplying drugs that led to the overdose death of former University of Maryland basketball star Len Bias. Tribble escaped arrest that night, but pleaded guilty yesterday to conspiracy to distribute cocaine.

Last week, Barry's attorney, R. Kenneth Mundy, filed a motion seeking a new trial, arguing that the sting was witnessed by two jurors and that they wondered at the time whether it was being staged for their benefit. Barry was arrested last January at the Vista Hotel in a controversial FBI sting.

The government's motion said that Mundy had relied on newspaper accounts of the event, and had not interviewed jurors to find out exactly what happened.

Even if he had done so, the motion said, and "assuming . . . that certain jurors did witness some type of law enforcement action, and assuming further that they knew what it was that they had witnessed, there has been no showing that these observations had anything to do with the defendant's trial or the jurors' consideration of the evidence."

The government's motion also strongly opposed Mundy's other argument: that Barry's conviction should be overturned because two of the U.S. marshals assigned to escort the jury into and out of the courtroom allegedly told the jurors that several of the dismissed alternates would have voted "guilty, guilty, guilty" had they been allowed to participate in the deliberations.

"Not every extraneous influence on the jury warrants a new trial," the government motion argued. Considering the fact that Barry was acquitted on one count and that the jury failed to reach a verdict on 12 other counts, it added, "it is manifest that the defendant was not prejudiced by the comment."

As for the misdemeanor count on which he was convicted, there was "overwhelming" proof of Barry's guilt, it said. That count involved his use of cocaine with an old friend and former civil rights colleague, Doris Crenshaw, at the Mayflower Hotel in November 1988.

Stephens also argued against Mundy's request to delay the mayor's scheduled Oct. 26 sentencing hearing, 11 days before Barry will stand for election to an at-large seat on the D.C. Council. Mundy had asked for a postponement in order to study Barry's pre-sentencing report.

"The government wishes to proceed to sentencing without unnecessary delay, because the community deserves to have a prompt resolution of this matter," the government's motion said.