Prosecutors May Compel Lewis to Testify : Securities: The U.S. is seeking information about the role of American Express officials in a manipulation of Fireman’s Fund stock.

Federal prosecutors have given former stock speculator Salim B. (Sandy) Lewis immunity from further prosecution and are expected to force him to testify about any role that top officials of American Express Co. may have played in the 1986 manipulation of Fireman’s Fund Corp. stock.

Lewis pleaded guilty in August to three felony counts related to the incident. He was sentenced to three years on probation, fined $250,000 and ordered to perform community service at a drug rehabilitation center.

Prosecutors are known to be interested in whether the manipulation was part of a conspiracy that involved James D. Robinson III, American Express’ chairman and chief executive, and Howard L. Clark Jr., the company’s former chief financial officer. Earlier this week, Clark was named chief executive of Shearson Lehman Hutton Inc., the Wall Street securities firm in which American Express owns a 61% stake.

Lewis admitted bidding up the price of Fireman’s Fund stock in May, 1986, one day before American Express sold 8 million shares of the insurance concern’s stock to the public. The manipulation increased American Express’ return from the sale. The government had charged that Lewis’ illegal actions were motivated by a desire to help Robinson and American Express, with which he had a longstanding business relationship.

Robinson and Clark weren’t accused of any wrongdoing. But sources said the government has telephone records showing that Lewis had phone conversations with the two executives shortly before the manipulation. Prosecutors want to put Lewis before a grand jury to testify about what was said in those conversations.

Stanley Arkin, a lawyer representing Lewis, refused to comment Friday.

Lawrence Armour, a senior vice president for American Express, said: “We have conducted thorough investigations, and we are satisfied that no one at American Express participated in any improper arrangement with respect to Fireman’s Fund securities.”