Maurice Hank Greenberg, former chief executive of insurer AIG, avoided direct answers in court testimony on Tuesday about a large block of AIG stock given decades ago to a private company he runs.

Ownership of the stock, once worth at least $20 billion, is the subject of a lawsuit pitting American International Group Inc against Starr International, a private investment firm of which Greenberg is chairman.

AIG accuses Greenberg of illegally taking the stock in 2005, the year he was forced out as AIG CEO.

On the witness stand in U.S. District Court, Greenberg was asked by AIG lawyer Ted Wells if $110 million in stock from an AIG predecessor company given to Starr in the 1970s was the stock the parties are dueling about in the lawsuit.

Apparently, replied Greenberg, who rarely made eye contact with his questioner.

At another point, in reference to a document that said the stock was for past and future generations, he was asked if that meant AIG employees.

Greenberg, 84, who was accompanied in court by his wife Corinne, said it meant past generations of AIG employees. But as to future generations, he said, No, I would not go so far as to say that.

AIG contends the shares were pledged to fund a deferred compensation program for selected employees. Starr disputes that, saying the beneficiary of the shares was always a charitable trust.

U.S. District Judge Jed Rakoff has ruled that the circumstances of Greenberg's ouster at AIG, the government bailout of the company last year, and controversial bonuses paid to AIG executives cannot be brought up at the jury trial, calling those matters irrelevant to the AIG lawsuit against Starr.

Greenberg left AIG amid probes of its accounting practices.

On Monday, Wells, in opening remarks at the trial, portrayed Greenberg as vindictive after he was ousted as CEO, spitefully cutting off a lucrative deferred compensation plan that had enriched AIG managers for the past 35 years.

Greenberg was AIG's chief executive for 38 years. He was known for a razor-sharp memory and was famed at AIG for his uncanny ability to track events throughout the company even though it had operations in 120 countries.

But on Tuesday he disclosed little first-hand knowledge of events he was questioned about.

Asked about a letter, he replied at various times, That's what it says.

Asked if he remembered writing a letter, he said, I'm a little older now than when I wrote those letters. I don't recall as easily.

The matter is in court because there is no written documentation of a trust to benefit employees. AIG maintains there is proof of an oral contract from Greenberg himself.

The insurer is seeking to wrest back $4.3 billion in proceeds from sale of AIG stock, and remaining shares which it says it will hold to fund a similar compensation plan.

The case is Starr International Company Inc v American International Group Inc 05-6283 in U.S. District Court for the Southern District of New York (Manhattan)

(Reporting by Lilla Zuill; editing by John Wallace)