The U.S. government's rescue of American International Group Inc. (AIG) and the long-term plans to pay back taxpayer funds remain shrouded in secrecy, U.S. lawmakers asserted Wednesday, chiding the firm for not being forthcoming with answers.

"I was surprised and disappointed to see that AIG continues to argue for secrecy," said Rep. Edolphus Towns, D-N.Y., chairman of the House Oversight and Government Reform Committee.

"We are not willing to let $180 billion go just on trust," Towns added.

Lawmakers took aim at both the embattled insurer and the AIG Trust, the three-member board overseeing the government's 80% ownership stake in the firm. Key to the question is the role of the Federal Reserve Bank of New York, which set up the AIG Trust, said Rep. Darrell Issa, R-Calif., the panel's ranking Republican. He called the three-member board "an unconstitutional and unaccountable entity."

"It is inappropriate for shadowy regulators and bureaucrats to use any legal sleight-of-hand to obscure their influence in running the U.S. financial sector," Issa said.

The tension was highlighted by an early line of questioning to AIG Chief Executive Edward Liddy. Lawmakers pressed him for the details of "Project Destiny," an AIG business plan that the firm had already provided details of to the Federal Reserve and the Treasury Department. Liddy balked at the request, saying the plan contained commercially sensitive information.

That claim did not sit well with Towns and Issa, who noted that information provided to the Fed and Treasury should not be withheld from Congress. Liddy relented, but only after consulting with his attorney and receiving assurances from lawmakers the information would be protected.

The broad question for lawmakers was whether the company will ever be able to repay taxpayers for the aid put forth to prop up the firm. Liddy, when pressed for a guarantee that the government would not have to give AIG more money and that taxpayers would receive a 100% return on their investment, said he couldn't do either.

"The answer is very dependent on what happens to the overall financial marketplace," Liddy said. While the government aid received so far should be "sufficient" and the company's stated goal is to repay the U.S. government, it will depend on asset values and the health of the overall economy, he said.

"It will take somewhere between three and five years," Liddy said of repaying the government, assuming the economy does not deteriorate further.

Liddy also said the firm hopes to make "material progress" on the immense amount of counterparty contracts it still has outstanding. He said the counterparty exposure, which at its zenith reached $2.7 trillion, was at $1.5 trillion at the end of the first quarter. By the end of the year, that figure should be "materially smaller."

-By Michael R. Crittenden, Dow Jones Newswires; 202-862-9273; michael.crittenden@dowjones.com