New York Attorney General Eliot Spitzer said yesterday he believes billionaire investor Warren Buffett could “shed light” on transactions involving the former chief executive officer of American International Group, which is now at the center of federal and state probes.

Mr. Buffett, who heads Berkshire Hathaway, will speak today with regulators as part of an investigation by Mr. Spitzer and the Securities and Exchange Commission into allegations of accounting improprieties at AIG.

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

“We believe [Mr. Buffett] can shed light on a series of transactions that … Hank Greenberg participated in,” Mr. Spitzer said in an interview with ABC’s “This Week.”

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

The Times said the modification was detected by Berkshire Hathaway-hired lawyers doing an audit of General Re in connection with an unrelated case.

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

“He is a witness in our view, and the focus of this investigation is AIG and the much broader reach of the offshore entities that AIG has created that we believe were, in many respects, fraudulent,” Mr. Spitzer said.

In a recent television interview, Mr. Greenberg’s attorney, David Boies, said AIG’s accounting, while perhaps wrong, neither greatly influenced the market nor misled people.

“Well, obviously I disagree with that,” Mr. Spitzer said Sunday. “The evidence is overwhelming that these were transactions created for the purpose of deceiving the market. We call that fraud. It is deceptive. It is wrong. It is illegal.”

Still, Mr. Spitzer would not say an indictment was forthcoming.

“We have powerful evidence. We will proceed with it,” he said. “It could be civil. It could be criminal.”

When asked whether he believed Mr. Buffett’s reputation will remain intact, Mr. Spitzer replied, “I sure hope so …Warren Buffett is an icon. He has succeeded the right way. He stands for smart, long-term investing, transparency, accountability – all those things we value and support.”

Mr. Buffett, whose Berkshire Hathaway owns The Buffalo News, was subpoenaed in January and has said he would cooperate.

Mr. Buffett did not immediately return a telephone message seeking comment that The Associated Press left on his company’s voice mail Sunday.