The General Accounting Office cannot fully account for $15 million of the $27 million in humanitarian aid that Congress sent to antigovernment rebels in Nicaragua this year, Rep. Michael D. Barnes (D-Md.) said yesterday.

Barnes told the House Foreign Affairs Committee that "the GAO now estimates that its final accounting will show that $15 million of the $27 million will have disappeared from sight in this way."

"This whole operation is completely out of control," Barnes added.

Joan McCabe, associate director of the GAO's national security division, emphasized yesterday that inability to verify the validity of receipts was "far different from saying the funds have disappeared from sight." She said she could not confirm Barnes' $15 million figure, which the congressman apparently received informally, until the final accounting is completed in mid-May.

The $15 million is more than double a GAO estimate two months ago when less money had been disbursed to the rebels, known as counterrevolutionaries or contras. A GAO official testified March 5 before Barnes' subcommittee on Western Hemisphere affairs that the congressional financial watchdog agency could not "verify actual delivery or receipt of items" involving $7.1 million of the aid disbursed before that date.

The official, Frank C. Conahan, director of the national security division, said the State Department lacked "procedures and controls" in Central America to monitor the movement of funds from Miami brokers to suppliers and the movement of purchased items to the contras.

However, he said, there was no evidence to suggest that the aid had not reached the contras.

Elliott Abrams, assistant secretary of state for Latin America, told the committee in March that the department can track all the expenditures but identification of the brokers and other personnel involved in the transactions is classified.

Barnes said the Nicaraguan Humanitarian Assistance Office, which is in charge of dispensing the $27 million, had been "forthcoming" in providing his subcommittee with all available documents in response to a resolution of inquiry voted last month. "The results of our investigation are very disturbing," he added.

"We have no way of knowing what happened to the funds deposited in Miami bank accounts for local purchases in Central America," Barnes said. "It is therefore quite possible for U.S. funds to have been used for the purchase of weapons and other items specifically prohibited by law."