A Canadian author sued Nobel Peace Prize winner and Iranian human rights activist Shirin Ebadi yesterday, saying she reneged on getting a publisher for a book they had written after she was warned that the book’s publication might spoil sales of her other books.

Shahir Shahidsaless, a Canadian citizen who lives in Toronto, and his wife, Faranak Shakoori, filed the lawsuit in U.S. District Court in Manhattan, seeking at least $1.3 million to cover the cost of writing a book with Ms. Ebadi that remains unpublished.

According to the lawsuit, Mr. Shahidsaless spent 18 months working on the book, “A Useful Enemy,” a project that originated after Ms. Ebadi wrote a preamble for the Iranian edition of “Sun in the Mist,” a book in Farsi published in Germany in 2003 and in Iran in 2004.

Mr. Shahidsaless said Ms. Ebadi suggested in a November 2004 telephone call that they co-write a book in response to Samuel Huntington’s “Clash of Civilizations” theory, which some have used to argue that Islamic and Western societies are culturally incompatible.

Mr. Shahidsaless said Ms. Ebadi specified the themes and chapters of the book and proposed a month later to write a chapter that dealt with Islam and its compatibility with the United Nation’s Universal Declaration of Human Rights, which she did, the lawsuit said.

Mr. Shahidsaless said in the lawsuit that he and Ms. Ebadi regularly spoke in person, by telephone, e-mail, and express mail about the content and style of the book after it was agreed that Mr. Shahidsaless would write the other parts of it with Ms. Ebadi’s input and approval.

In January 2006, Ms. Ebadi and Ms. Shahidsaless were meeting at a Manhattan hotel when Ms. Ebadi mentioned that she had signed a contract to publish her memoir, “Iran Awakening: A Memoir of Revolution and Hope,” the lawsuit said.

According to the lawsuit, the writers agreed that Ms. Ebadi would approach Random House, which was publishing her memoir, and ask them to publish the co-written book and give the writers an advance of $1 million.

In July 2006, Ms. Ebadi sent an e-mail to Mr. Shahidsaless saying that her literary agent and Random House had recommended she not publish the book because it would damage sales of her future books, the lawsuit said.

Messages left for comment with Random House and Ms. Ebadi’s agent, Wendy J. Stothman, were not immediately returned.

In a subsequent e-mail, Ms. Ebadi referred to self-interested political motivations as her reason for breaching her agreement with Mr. Shahidsaless to publish the book as a co-author, the lawsuit said.

The lawsuit said Mr. Shahidsaless has lost at least $1 million because the book was not published and because he has not received the fame and notoriety that would have enabled him to publish other books.