Gupta, a one-time global head of the McKinsey & Co consultancy firm, is the most prominent corporate executive charged in the U.S. government's broad investigation of Wall Street insider trading, a probe that used secretly recorded phone conversations as evidence.

His trial is scheduled to start on April 9 in U.S. District Court in New York. Gupta, 63, has denied the charges of securities fraud and conspiracy in providing inside tips about Goldman and Procter & Gamble board meetings to hedge fund founder Raj Rajaratnam.

At a hearing in federal court in New York to discuss potential evidence and potential witnesses, U.S. prosecutor Reed Brodsky identified Ajit Jain, the top Berkshire Hathaway insurance executive, as a "close friend" of Gupta who has already been interviewed by the prosecution and defense.

Jain is not accused of any wrongdoing.

A spokeswoman for renowned investor Warren Buffett's company Berkshire Hathaway did not immediately respond to a request for comment. Jain, who heads the company's insurance business, has been identified as a possible successor of Buffett's as chief executive.

Dozens of hedge fund managers, lawyers and executives have been convicted since 2009 in the sweeping prosecution, including Gupta's onetime friend and business associate Rajaratnam. He is serving an 11-year prison sentence.

Goldman Sachs chief executive Lloyd Blankfein testified at Rajaratnam's two month-long trial last year and could be called to the witness stand in Gupta's case along with other Goldman executives, according to court records.

On Friday, the name of Goldman board member Claes Dahlback also came up in court and he could be asked to testify.

"After Rajaratnam was arrested in October 2009, Dahlback asked Gupta if he knew Rajaratnam," U.S. District Judge Jed Rakoff said, reading from a government report on the case. "Gupta responded that Rajaratnam was a 'bad man' and further stated that Gupta lost money with Rajaratnam."

A Goldman Sachs spokesman, David Wells, declined to comment.

Government investigators recorded at least two discussions between Rajaratnam and Gupta.

Gupta's lawyer Gary Naftalis indicated that part of the defense would be to emphasize that in 2008 and 2009 - the time the alleged illegal tips took place - relations between Gupta and Rajaratnam had deteriorated. He said Gupta lost all of a $10 million investment he made with the Galleon hedge fund manager.

"We were very unhappy with how he handled our investment and the information he gave us and this is obviously inconsistent with going out and tipping him," Naftalis told the judge.

The government contends that Gupta provided Rajaratnam with advance knowledge of Warren Buffett's $5 billion investment in Goldman at the height of the 2008 financial crisis, as well as information about Goldman's surprise fourth-quarter loss in 2008 and P&G's quarterly earnings in late January 2009.

The case is USA v Gupta, U.S. District Court for the Southern District of New York, No. 11-907.

(Reporting By Grant McCool; Editing by Gary Hill)

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