The insurance giant has accused Greenberg of plundering an AIG retirement program of billions of dollars.

AIG called Greenberg to the witness stand early Tuesday afternoon in federal court in Manhattan. The company says Greenberg improperly took $4.3 billion in stock from the company in 2005.

AIG's lawyer Theodore Wells says Greenberg took the stock because he was angry he was ousted by the company amid investigations of accounting irregularities. David Boies, the lawyer representing Starr International, the firm where Greenberg is now chairman, says the stock belonged to Starr.

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NEW YORK (AP) - Witnesses begin testifying Tuesday in the civil trial of American International Group Inc.'s former top executive, accused of plundering an AIG retirement program of billions of dollars.

Attorney Theodore Wells told jurors Monday in Manhattan that former Chief Executive Officer Maurice "Hank" Greenberg improperly took $4.3 billion in stock from the company in 2005, after he was ousted by the company amid investigations of accounting irregularities.

"Hank Greenberg was mad. He was angry," Wells said in U.S. District Court of the emotional state of the man who, over a 35-year-career, built AIG from a small company into the world's largest insurance provider. He said the saga is a story of "anger, betrayal and cover-up."

Wells said that Greenberg, within weeks of being forced out in mid-2005, gave the go-ahead for tens of millions of shares to be sold from a trust fund. The fund was set up decades ago to provide incentive bonuses to a select group of AIG management and highly compensated employees that they would receive upon their retirement.

Wells showed the jury several clips of Greenberg speaking on videotape about the responsibilities of the trust fund. He called it Greenberg's "videotaped confession."

Wells asked the jury to award AIG $4.276 billion and 185 million AIG shares.

Greenberg, 84, has contended through his lawyers that he had the right to sell the shares because they were owned by Starr International, a privately held company he controlled.

Greenberg's lawyer, David Boies, told the jury in his opening statement that the shares sold by his client did not belong to AIG.

"I disagree with a great many things that Mr. Wells said," Boies told the jury. He said a study of the documents in the case would prove that the shares sold by Greenberg did not belong to AIG.

"Look in this case not to what people said after this lawsuit started," Boies said. "Look to what they said and did and wrote before the lawsuit started."

Starr International was named after Cornelius Vander Starr, who created a worldwide network of insurance companies in the early 1900s.

AIG maintains that Starr and Greenberg, his protege and successor, decided in the late 1960s to organize the various companies under one holding company, AIG.

Starr International remained a private company and its shareholders decided in 1970 that the amount that its shares of AIG were worth above book value of about $110 million should be used to compensate AIG employees, AIG has said.

The embattled insurer is trying to reclaim the money from Starr it says was wrongly pocketed through stock sales by Greenberg.

The trial relates to events that occurred long before AIG found itself under attack earlier this year over its bonus program.

The company was roundly criticized after it accepted $182 billion in federal aid and then paid out $165 million in bonuses to employees, including traders in the financial products unit that nearly caused the company to collapse.

Before the jury was chosen Monday, U.S. District Judge Jed S. Rakoff said evidence in the trial could not include information about the government bailout. He also said the entire trial will last no longer than a month. Greenberg is among one of several witnesses expected to take the stand this week.

The trial features two legal heavyweights.

Boies argued on behalf of Democratic presidential candidate Al Gore before the U.S. Supreme Court during the disputed presidential vote in 2000. Wells was on the team of defense lawyers in 2007 for former White House aide I. Lewis "Scooter" Libby, who was convicted of perjury, obstruction and lying to the FBI about his role in leaking the name of a CIA operative to a reporter.