NEW YORK (Reuters) - Lawyers for Rajakumara Rajaratnam, the billionaire founder of Galleon hedge fund accused of insider trading, said the US government's case is weak and they were confident of winning any trial, according to a letter filed in court yesterday.

Rajaratnam's lead lawyer, John Dowd, asked a Manhattan federal court magistrate judge to reduce his client's bond to $25 million from $100 million and to modify his travel restrictions, arguing he had no incentive to flee because of strong family ties to the United States and $30 million in property.

"The idea that Mr Rajaratnam would simply abandon those properties to avoid a trial that he is confident of winning is neither realistic nor credible," Dowd, a high-profile Washington lawyer, said in a letter to Magistrate Judge Frank Maas.

Sri Lankan-born Rajaratnam, 52, was arrested on October 16, along with five others in what US prosecutors described as the biggest hedge fund insider trading case ever. The case marked the first time court-approved telephone wire taps were used in a white-collar crime investigation, prosecutors said.

Yesterday's letter said Rajaratnam's lawyers have conferred with the government "which does not consent to this request".

A spokeswoman for the US Attorney in Manhattan, which brought the criminal charges, declined to comment.

The US Securities and Exchange Commission filed civil charges against the six, who included employees of some of the most prestigious companies in the United States.

Federal prosecutors have said that the purported insider trading scheme yielded a profit of more than $20 million.

All six were released on bond. Rajaratnam's bond was $100 million and his travel restricted to within 110 miles of New York City. Yesterday, lawyers asked the judge to give him permission to travel all over the US.

"The case is at its earliest stages, and the Government does not yet have the critical information that will place its current allegations in the proper context and dispel any allegation of criminal conduct," Dowd and lawyers at his law firm Akin Gump said in the letter.

"Moreover, the strength of the Government's evidence, which relies heavily on a single cooperating witness widely reported to be Roomy Khan, has been assailed in a series of recent articles published in the New York Times and Wall Street Journal."

The letter cited reports in those newspapers that said Khan, a former employee of Intel, was a convicted felon.

Galleon liquidated most of its $3.7 billion portfolio last week after investors began demanding their money.