NEW YORK — A 91-year-old former chief executive of insurance company AIG seemed eager to defend himself Tuesday against civil fraud charges, insisting he had no reason to attempt to hide several hundred million dollars in losses from the auto warranty wing of a mammoth business operating in 137 countries.

During testimony in state Supreme Court in Manhattan, Maurice Greenberg said American International Group Inc.’s accountants and lawyers did explore in 1999 and 2000 how to convert the large insurance underwriting loss in the auto warranty business into an investment loss.

Assistant Attorney General David Nachman asked the former multi-decade AIG chief executive if converting underwriting debt into investment debt would allow the company to report higher underwriting income and lower investment income.

“It could be,” he said. “I don’t know.”

New York state has accused Greenberg and AIG’s former chief financial officer of manipulating AIG’s accounting records in 2000 and 2001 to hide hundreds of millions of dollars in losses from investors.

The state wants state Supreme Court Justice Charles E. Ramos, who is hearing the trial without a jury, to ban Greenberg from working in the securities industry or as a public company executive. It also seeks $53 million, including bonuses Greenberg received in the years he was alleged to have manipulated the company’s finances.

Greenberg said he wasn’t concerned about the company’s bottom line in 1999 because the losses were such a small part of the company’s operating revenue.

“It was a minor effect on our overall results,” the World War II and Korean War veteran said during daylong testimony that was set to resume Wednesday.

He said he got immersed in the troubles with the auto warranty business “to teach a lesson to management that had concocted a bad deal and had to learn from that.”

“The main issue for me from the beginning was to teach a lesson to our people,” Greenberg said.

Nachman cited email and other correspondence Greenberg had between 1999 and 2002 to refresh his memory about the auto warranty program and told Greenberg that he suspected he had reviewed the materials himself as he dealt with the state’s accusations and prepared for trial.

But Greenberg was dismissive of the litigation, saying “other things are far more important than this.”

He added: “I did not think this was an important matter for me,” especially since it occurred more than 15 years ago.

AIG, one of the world’s largest insurance companies, nearly collapsed in the fall of 2008 at the height of the financial crisis and received about $180 billion in bailout aid from the government.

Greenberg was forced out in 2005 after leading the company for more than 37 years after he replaced founded C.V. Starr, who died in 1968.