The Pentagon cannot account for substantial quantities of weapons and equipment used in Central American training exercises last year, prompting congressional concern that the materiel might have been left for Nicaraguan rebels.

An Army audit report, obtained yesterday, criticized the U.S. military's failure to monitor the use of guns, ammunition, fuel, repair parts, clothing and medicine in the 1986 training exercises.

The audit was of a $38.3 million road-building exercise, Blazing Trails 86, which involved 10,000 Army Reservists and National Guard members in Honduras and Panama.

The February audit report said the Pentagon's weak controls left an undetermined quantity of arms and ammunition in Central America "susceptible to diversion and unauthorized use."

Rep. Barbara Boxer (D-Calif.), citing the "shocking pattern of sloppy management {and} waste" reported by auditors, voiced concern in a Nov. 3 letter to the inspector general's office that the Pentagon might have sought "to provide unauthorized funding or aid" to the Nicaraguan contras or the governments of Honduras or Panama.

Pentagon spokesman Lt. Col. John Chapla denied that the Defense Department used the training exercises "to orchestrate a massive diversion" of weapons.

Chapla acknowledged there was mismanagement of the exercises but attributed it to the inexperience of many of the Army Reserve and National Guard participants.

The Army Audit Agency reported that it could not determine with certainty how much U.S. military equipment was lost, stolen or diverted because so many U.S. records were inaccurate or unreliable.

Testimony at the congressional Iran-contra hearings last summer showed that the Aguacate air base in Honduras, built for U.S. training exercises in 1985, was being used by the contras.

The rebels, many of whom are based in Honduras, relied on the Central Intelligence Agency and a private aid network managed by Lt. Col. Oliver L. North of the National Security Council staff to shuttle supplies to and from Aguacate last year.

Army auditors also reported that:The Pentagon in effect subsidized the Honduran and Panamanian governments by not billing them at least $761,000 for expenses.

Many of the Reservists and Guard members did not receive proper training.

The Pentagon was unresponsive to auditors' recommendations for improving management of the exercises. Several management failures pointed out during the 1985 exercises recurred last year.