Assistant U.S. Attorney Andrew L. Fish asked the judge to delay a prior court session because "the parties are very close to completing plea negotiations."

"The Government anticipates that both defendants will be ready to enter guilty pleas on May 10, 2007," Fish wrote.

The case is the largest yet in a renewed effort by the Justice Department and the Securities and Exchange Commission to root out fraud that puts average investors at a disadvantage in the stock market.

Securities enforcers are probing unusual trading patterns in many companies' stock and options shortly before merger and buyout offers. Dow Jones said last week that it had received inquiries from regulators interested in trades preceding News Corp.'s recent bid for the company.

The Collottas are among more than a dozen defendants nabbed in a widespread insider-trading ring in March. Law enforcement authorities singled out the Collottas because of their special role in protecting the integrity of investment banks and the market as a whole.

Randi Collotta once served as an associate in Morgan Stanley's global compliance division, where she had access to secret information about pending deals involving such clients as Macromedia, Catellus Development, and PacifiCare Health Systems, according to the grand jury indictment against her.

Rather than safeguard the information, however, Collotta passed it along to her husband, also a lawyer, who shared it with co-conspirators, prosecutors said.

Kenneth Breen, a lawyer for Randi Collotta, said yesterday that she would "address these charges in court." Brian Rafferty, a lawyer for Christopher Collotta, declined to comment.