A former FBI agent, on trial for allegedly obstructing justice, was accused yesterday of improperly telephoning a government witness at her hotel room shortly before she was scheduled to testify against him.

The accusation was made by Lila Moran, a witness in the criminal trial of former agent H. Edward Tickel Jr. Moran testified in U.S. District Court in Alexandria that Tickel phoned her Wednesday evening and spoke with her for 15 minutes.

W. Gary Kohlman, one of Tickel's lawyers, later denied that the phone conversation had taken place.

He said Tickel was with him at a law office and not on the phone at the time of the alleged incident.

Tickel is prohibited by a court order from communicating with witnesses in his trial. Judge James C. Cacheris said he would not rule on whether the alleged phone call had occurred, but reiterated his warning that Tickel is barred from contacting witnesses.

Tickel, a former FBI specialist in undercover break-in techniques, is on trial on charges of dealing in stolen diamonds, evading taxes, obstructing justice and persuading his friends to commit perjury.

Moran, once a close friend of the former agent, testified that Tickel had warned her in the alleged phone call that she might be grilled about unseemly incidents in her personal life. But, she told the jury, "He said everything would be all right if I told the truth."