"I promised I would convene a press conference to open up new horizons and help in accusing Israel of the assassination of Rafik al-Hariri, and that is what I am doing," Arab and Israeli media quoted Nasrallah saying in a televised speech from his Beirut hideout.
His speech Monday night was extensively quoted on SANA, the Syrian national news agency Web site.
Nasrallah said Syrian President Bashar Assad had informed him of plans to withdraw Syrian troops from Lebanon prior to Hariri's assassination. Despite this, he said, Israel planned to kill Hariri because they wanted the Syrian Army out of Lebanon.
"Israel was looking for a way to assassinate Hariri in order to create political chaos that would force Syria to withdraw from Lebanon, and to perpetuate an anti-Syrian atmosphere (in Lebanon) in the wake of the assassination," Nasrallah was quoted saying.
To strengthen his claims he produced a videotape of a man called Ahmed Nasrallah, who was arrested in 1996 for allegedly spying for Israel.
"I met someone who worked with Rafik Hariri and I told him that Hezbollah wants to kill him (Hariri)," the man was heard saying in the tape, referring to an apparent attempt to turn Hariri against Hezbollah.
The Hezbollah chief asserted that as far back as 1993 Israel tried to convince Hariri that Hezbollah planned to assassinate him, he said.
During his speech, the Hezbollah leader presented news articles and videos of senior Israeli reporters to support his claims.