In an open letter to the Israel public, Prime Minister Benjamin Netanyahu promised to deliver a " tough response" in his UN speech on Thursday to Iranian President Mahmoud Ahmadinejad's address to the General Assembly a day earlier.

Netanyahu made the remarks as he left for the United States Wednesday evening.

In his address at the General Assembly earlier Wednesday, Ahmadinejad predicted the "elimination" of Israel and said Iran was under a "continued threat" by "uncivilized Zionists," who, he said, were trying to "resort to military action against our great nation."

The Iranian president made the remarks on the eve of the Jewish Yom Kippur (Day of Atonement) fast, the holiest day in the Jewish calendar.

Netanyahu said in his letter that "on Yom Kippur eve, sacred to the Jewish people, the Iranian tyrant chose to call publicly for us to vanish. It's a black day for those who chose to remain in the auditorium and hear those hateful words."

"In the statements I will make before the representatives, they will hear our response. I am working every way in order that Iran does not have nuclear weaponry," the Israeli prime minister said.

"On the question of Iran, we are all united in the goal of preventing Iran from achieving nuclear weaponry. On the day on which we pray to be inscribed in the Book of Life, a stage was given to the tyrannical regime of Iran which seeks at every opportunity to sentence us to death," Netanyahu said.

Netanyahu's aides told the Times of Israel website that the prime minister's speech, which will contain "significant" content, may undergo last-minute tweaking.

According to reports by local media, Netanyahu is expected to try and gather support at the United Nations for tougher sanctions on Iran.

The Ma'ariv newspaper reported Tuesday that Netanyahu would include in his speech the "red lines" he believes should be set before Iran that, if crossed, would prompt a military response.

"I will reiterate that the most dangerous country in the world must not be allowed to arm itself with the most dangerous weapons in the world," Netanyahu said at the weekly cabinet meeting on Sunday.