The commander of the Army's elite Delta force counterterrorist team told the Defense Department last month that an investigation into alleged financial irregularities by dozens of his men could impede a possible rescue attempt of passengers aboard the hijacked cruise ship Achille Lauro, according to informed sources.

The warning was delivered in the Pentagon by Delta commander Col. William Garrison to Gen. Max R. Thurman, the Army's vice chief of staff, after investigators arrived at Delta's headquarters at Fort Bragg, N.C., to question members of the unit, the sources said. Army leaders agreed to suspend the investigation, which includes allegations of more than $200,000 in double billings by members of the unit, until Delta force returned from the Middle East, the sources said.

One source said Garrison told Thurman that if his men were tied down at Fort Bragg by the financial inquiry, "he wouldn't have the operators he needed" for a possible rescue attempt.

There were reports at the time of the Achille Lauro hijacking that about 50 Delta force members landed in Sicily behind the Navy jets that intercepted the Egyptian plane carrying the pirates Oct. 10. Italian Prime Minister Benito Craxi said in a statement a week later that U.S. soldiers in combat dress who "were part of the Delta forces" poured from a C141 military transport plane and surrounded 50 Italian soldiers guarding the Egyptian plane.

Army spokesman Elaine Henrion said yesterday that Thurman had no comment and that "he doesn't even acknowledge there is a Delta force."

Last night, Garrison said in a telephone interview, "Col. Garrison does not have a spokesman but if I did I would tell him to say, 'Col. Garrison has no comment on that; as a matter of fact, he does not even acknowledge he exists.' "

Army sources said Garrison has disciplined more than 80 of his men by giving them nonjudicial punishments known as Article 15s. Several others are facing courts-martial, sources said.

The financial inquiry has focused on expenses incurred during the last three years when members of the Delta force were assigned temporarily overseas to protect U.S. ambassadors and were quartered by the State Department. More than 80 members of the unit allegedly submitted vouchers to the Army for living expenses that had been paid by the State Department.

The Delta inquiry is part of a wide-ranging Army investigation of alleged financial misconduct in the spending of more than $150 million on classified special operations and intelligence missions. One Army counterintelligence officer, Lt. Col. Dale C. Duncan, was indicted Tuesday in Alexandria on federal charges of defrauding the government of funds used in secret military operations.

Yesterday, Army prosecutors also began presenting evidence at Arlington Hall in the first court-martial connected to the sweeping investigation. Master Sgt. Ramon Barron, a former colleague of Duncan, has been charged with financial improprieties involving travel vouchers on classified missions.

Delta force members were deployed to the Middle East during the TWA hijacking in June, and have prepared for other potential hostage rescue attempts in the past few years, sources said. Delta's most prominent -- and only publicly acknowledged -- mission was the attempted rescue in April 1980, of the hostages held in the U.S. Embassy in Iran. That attempt failed, and eight members of the rescue force died in an aircraft accident in the desert.

The unit's formal name is the First Special Forces Operational Detachment-Delta (Airborne). About 300 men are assigned to the unit, sources said.

Garrison, who commanded an American contingent of the peacekeeping force in the Sinai Peninsula in 1982, became the Delta commander last summer. During most of the period covered by the financial investigation, the commander was Col. Sherman H. Williford, who since has been promoted to brigadier general. Williford could not be reached for comment last night at Fort Drum, N.Y.