The CIA helped undermine the Iran-Contra criminal investigation and bribed senior officials in Costa Rica, a former prosecutor charged.

The allegations are contained in a book by Jeffrey R. Toobin, a federal prosecutor in New York who worked for Iran-Contra special prosecutor Lawrence Walsh from 1987 to 1989.The book, "Opening Arguments," will be published in March, but galley proofs recently were provided to reporters. Toobin won a legal battle with Walsh, who argued unsuccessfully that the book would reveal grand jury secrets, compromise prosecution strategy and disclose classified information.