Maurice R. "Hank" Greenberg, American International Group's (AIG) former chief executive, took the stand Tuesday afternoon in a long-running dispute over control of a block of shares held by Starr International Co.

Greenberg, who was forced out as the insurer's top executive in 2005, is a key witness in a legal clash between Starr International, or SICO, and AIG over millions of AIG shares held by the one-time sister company to AIG.

"That is the stock the parties are feuding about?" asked Ted Wells, a lawyer for AIG, referring to shares that went to SICO in 1970 as part of a reorganization of AIG and its affiliates.

"Apparently," said Greenberg, dressed in a charcoal grey suit and pink tie.

AIG has sued SICO for $4.3 billion in damages - representing the sale of tens of millions AIG shares since Greenberg left the insurer - and the return of more than 185 million shares SICO controls.

The jury trial is being heard in U.S. District Court in Manhattan and is expected to last a month. Greenberg, who is SICO's chairman, could be on the stand for a lengthy period of time. AIG claims the shares were set aside in a trust to fund a deferred compensation plan for a select group of AIG executives and were improperly diverted by SICO and its management. About 1% of the company's employees and executives participated in the incentive plan.

SICO's lawyers have said the shares were placed aside for a number of purposes, including protecting AIG from a takeover bid, to go to charity if SICO were liquidated and to fund other projects. The decision on whether to fund the compensation program lied with SICO's voting shareholders, which include Greenberg.

"If the people do well, the company does well and SICO does well," Greenberg said during his testimony Tuesday.

The initial questioning of Greenberg focused on a document he signed in 1992, which discussed the history of the 1970 reorganization and the use of the SICO's block.

SICO initially received about $110 million in stock. The shares had grown in value to $2.5 billion in 1991 and were worth as much as $20 billion at one point.

However, AIG's stock has been under pressure in the past year and the company had to seek government assistance to avoid collapse last year.

Earlier Tuesday, David Boies, a lawyer for SICO, said in his opening statement that it was only after AIG had filed the lawsuit that it began to make the claim that the trust was designed to benefit AIG.

"They were telling everybody internally and externally these were SICO shares," Boies said. "They could do anything they wanted with them."

Boies said the pledge made by SICO's voting shareholders, including Greenberg, was to preserve the value of the shares for use by SICO and to ultimately go to a charity when the company is resolved.

The voting shareholders "were obligated not to take it for themselves," Boies said.

After Boies completed his opening statement, jurors got their first taste of Greenberg as AIG introduced videos of speeches he gave in 1996 and in 2000 to AIG employees and talked about the deferred compensation program.

In the 1996 speech, Greenberg said the purpose of the program was to "provide an incentive for future generations" of AIG managers and employees.

In the speech, Greenberg said he and the other voting shareholders in 1970 were entitled to take the shares as their own, but instead set aside the stock to fund the compensation program.

"It was the most unselfish act in corporate history that I know of in this country," Greenberg said in the speech.

-By Chad Bray, Dow Jones Newswires; 212-227-2017; chad.bray@dowjones.com -