The statement did not say when the formal indictment would be filed, but local media reports said it would be within days.
Zion Amir, Katsav's attorney, said that the defence team was "preparing for a long struggle to prove the innocence of the former president".
Katsav, the eighth president of Israel, resigned in July 2007 as part of a plea agreement which granted him immunity from the rape charge and a possible 20 year jail sentence, but required him to plead guilty to sexual harrassment.
However, Katsav later reneged on the deal.
Katsav, who was replaced as president by Shimon Peres, has said that he is a victim of a political witch hunt. He has always denied any wrongdoing.
The affair that began in July 2006, when Katsav filed a complaint with the attorney general alleging that a former employee was trying to blackmail him.
However, an investigation resulted in the woman, referred to by the Israeli media as Plaintiff A, accusing the father of five of raping her while she was his secretary in the late 1990s.