Strauss-Kahn, 62, was a steward of the world economy and a leading candidate for the French presidency when he was arrested on May 14 and charged with assaulting a hotel maid in New York.

The arrest forced Strauss-Kahn's resignation from the International Monetary Fund and appeared to end his presidential ambitions, but his political career could be revived if prosecutors drop their case against him.

In a dramatic turnabout, a source familiar with the case said on Thursday night that prosecutors now had doubts about the maid's credibility as a witness.

"The credibility is in question," the source, speaking on condition of anonymity, told Reuters.

From the start, the case hinged on the purported victim, a 32-year-old Guinean immigrant who cleaned the US$3,000-a-night suite at the Sofitel hotel in Manhattan where Strauss-Kahn was staying.

Strauss-Kahn was due back to court in New York on Friday to seek changes to his bail conditions, defense attorney Benjamin Brafman said.

Strauss-Kahn resigned from the IMF on May 19 and pleaded not guilty on June 6, vehemently denying the allegations. He faces up to 25 years in prison if convicted.