Albany, N.Y. ? Billionaire investor Warren Buffett is merely a witness who could “shed light” on transactions involving the former chief executive of insurer American International Group Inc., which is now at the center of federal and state probes, New York Atty. Gen. Eliot Spitzer said Sunday.

Buffett, who heads Berkshire Hathaway, will meet today in New York with regulators as part of an investigation by Spitzer and the Securities and Exchange Commission into allegations of accounting improprieties at AIG involving a unit of Buffett’s company.

The company’s former CEO, Maurice “Hank” Greenberg, was forced out in mid-March as those allegations mounted. Greenberg is scheduled to speak with regulators on Tuesday.

“We believe (Buffet) can shed light on a series of transactions that … Hank Greenberg participated in,” Spitzer said in an interview with ABC’s “This Week” television program.

Spitzer stressed that Buffet was “not a subject or a target of our investigation,” but said, “There are some ambiguities that will be hopefully addressed (today) in our discussion with Mr. Buffett.”

Buffett was subpoenaed in January and has said he would cooperate.

The New York Times reported Friday that documents from a 2000 reinsurance transaction at the center of the probes had been doctored months after the deal was struck. The newspaper cited unnamed executives, who said the deal was “repapered” by midlevel employees of General Re Corp., a unit of Omaha, Neb.-based Berkshire Hathaway.