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., a one-time sister company to AIG.

Greenberg is a key witness in the dispute between Starr International, or SICO, and AIG over tens of millions of AIG shares held by SICO.

AIG has sued SICO for $4.3 billion in damages - representing the sale of tens of millions AIG shares since he 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 was forced out of AIG in 2005 amid investigations into the insurance company's accounting, is SICO's chairman.

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