Prosecutors will agree to drop the charges against Dominique Strauss-Kahn - either on his next court date in two weeks or even sooner, according to a top investigator in the case who called the eventual dismissal "a certainty."

"We all know this case is not sustainable," The New York Post exclusively quoted a source, who is at the center of the investigation and would speak only on the condition of anonymity.

"Her credibility is so bad now, we know we cannot sustain a case with her," the source said, referring to the Guinean hotel maid who accused Strauss-Kahn of trying to rape her in his plush Midtown hotel suite - shocking charges that got the international banker bounced as head of the IMF and also derailed, at least for now, his bid to become president of France.

"She is not to be believed in anything that comes out of her mouth - which is a shame, because now we may never know what happened in that hotel room," the source said. "Did [Strauss-Kahn] use force? Was there actually a crime? I don't think we'll ever know."

Meanwhile, French lawyers for Strauss-Kahn promised to fight back with criminal charges of their own against a French writer who claims he tried to rape her nearly a decade ago.