On Sunday, police had said that a weeks-long investigation produced enough evidence to indict the 60-year-old married father of five for rape, sexual harassment and wire-tapping.
Under enormous pressure to resign from his largely ceremonial post, Katsav opted out of opening parliament's new session Monday after lawmakers threatened a boycott -- the first time in Israel's 58-year history that a session began without the head of state.
Katsav had originally said he would preside over the opening despite the police statement, but later cancelled his appearance after a wave of protests from lawmakers.
Katsav, who became head of state in 2000, is immune from prosecution while president but could be charged if impeached by the Knesset.
"There is sufficient evidence indicating that in several cases ... the president carried out acts of rape, forced sexual acts, sexual acts without consent and sexual harassment," police said.
"There is sufficient evidence indicating violation of the law banning wire-tapping by the president," they added after a meeting with investigators and Attorney General Menachem Mazuz.
Katsav, who was born in Iran, has rejected calls to resign while the investigation continues and repeated his denials of the allegations.
"The president was surprised and shocked by the police recommendations," a statement from his office said. "He repeats that he is a victim of a plot and that sooner or later the allegations against him will be proven false."
Mazuz is expected to decide within two to three weeks whether to file an indictment against Katsav and public radio reported that the president was weighing his options.
Katsav's attorney Zion Amir predicted that Mazuz would not file formal charges against his client.
"This is not the first time police have recommended the indictment of senior figures, including prime ministers, and those recommendations have all been rejected," he said.
But "if Mazuz opts for an indictment, I think the president will have no other choice but to resign", Amir said.
Katsav, a member of the right-wing Likud party, could face between three and 16 years in prison if convicted, Israeli radio reported.
The charges are the most serious faced by an Israeli leader, although several other top figures, including former prime minister Ariel Sharon, have faced probes into allegations of corruption.
Police have investigated no fewer than 10 complaints of rape and sexual harassment by former Katsav employees during his presidency and as tourism minister and now say that an indictment could be filed in three or four of these cases.
Katsav has been under criminal investigation since July, when a senior female aide complained she was sexually harassed while working under him. The president filed a simultaneous complaint against the aide for extortion.
But police said Sunday that there was no substantial evidence to back accusations by Katsav's legal team that one of the complainants attempted to blackmail him over the rape allegations.
If Katsav is forced out of office, he will become the second Israeli president in a row to resign amid scandal.
His predecessor, the late Ezer Weizman, resigned after revelations that he received around 450,000 dollars as "gifts" from French millionaire Edouard Saroussi in the 1980s, when Weizman was a member of parliament and minister.
The Katsav case is the latest blow to Israel's leadership, with Prime Minister Ehud Olmert's government steering its way through public anger over failings in its 34-day war against Hizbullah in Lebanon.

Copyright AFP (Agence France-Presse), 2006