The Secret Service is preparing to require new agents to sign a pledge that they will not discuss what they see and hear while protecting a president, Director Brian Stafford said yesterday.

After at least one former agent discussed ex-intern Monica S. Lewinsky with reporters and a retired member of President John F. Kennedy's protective detail revealed Kennedy's sexual trysts to author Seymour Hersh, the Secret Service is reviewing a pledge of confidentiality as a condition of employment.

"In over 100 years, we never felt that there was a need to do that," Stafford said in an interview with the CBS News program "Saturday Morning."

"It was just a code that we all thought and felt very strongly about and didn't feel that we had to reduce it to paper," he said. "But we are now."

"Our legal people are now looking at a confidentiality statement, which new employees will be required to sign," Stafford said.

Stafford, who became director four months ago, also told CBS that he will urge Congress to exempt agents from being subpoenaed and forced to testify, as they were by independent counsel Kenneth W. Starr as part of his probe of the Lewinsky affair.

"When there's a new president, if they don't trust us, they don't have confidence in us, then we won't be able to do our job well and they will push us back," Stafford said.