Because of the debate in Washington over defectors' credibility, Mr. Haideri was not interviewed by American intelligence agents until months after he left Iraq. Richard Perle, chief of the Defense Policy Board, which advises the Pentagon, and a leading hard-liner on Iraq, said that until recently, C.I.A. officials were so hostile to defectors brought out of Iraq by the Iraqi National Congress, the umbrella opposition group, that they refused to interview them and even tried to discredit their information. "But ultimately, the flow of information was so vital and so overwhelming that they could no longer ignore it," Mr. Perle said.