JERUSALEM, Sept 26 (Reuters) - Prime Minister Benjamin Netanyahu on Wednesday promised a tough response at the United Nations to the latest verbal attacks on Israeli by Iranian President Mahmoud Ahmadinejad and said he was determined to stop Iran developing nuclear weapons.

Before boarding a flight to New York to address the annual U.N. General Assembly, Netanyahu issued an open letter to Israelis marking the end of Yom Kippur, the Day of Atonement, the most sacred holiday in the Jewish calendar.

"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.

"On Yom Kippur eve, sacred to the Jewish people, the Iranian tyrant chose to call publicly before all of the world for us to vanish. This is a black day for those who chose to remain in the auditorium and hear these hateful words."

The Israeli leader did not name any U.N. member state in particular. The United States delegation chose not to attend Ahmadinejad's General Assembly speech, while other allies of Israel walked out.

"In statements I will make before representatives of the nations at the U.N. General Assembly, they will hear our response. As prime minister of Israel, the state of the Jewish people, I am working in every way in order that Iran does not have nuclear weaponry," Netanyahu said.

"History proves that those who wanted to wipe us off the map failed in that objective, while the Jewish people overcame all obstacles."

Jews believe that between Rosh Hashana (the Jewish new year) and Yom Kippur, God decides who will be inscribed in the Book of Life, meaning who will not die in the coming year.

Ahmadinejad's speeches in the U.N. forum included a prediction that Israel would be "eliminated".

On Wednesday, with Israelis observing a solemn silence for Yom Kippur, he told the Assembly that Iran was under a "continued threat by the uncivilized Zionists to resort to military action against our great nation".

Iran denies working in secret to develop nuclear weapons, saying that it is building a peaceful atomic power capability. Israel and its main ally the United States have repeatedly said they will not permit Tehran to build the bomb.

Netanyahu's senior advisers privately shrug off Ahmadinejad's incendiary rhetoric, saying he has no policy-making role in Iran's nuclear development programme.

On Tuesday, U.S. President Barack Obama told the U.N. Assembly that time was running out to find a diplomatic solution to the Iranian nuclear issue. "The United States will do what we must to prevent Iran from obtaining a nuclear weapon," he said.

That statement went no further than his previously stated position, appearing to ignore calls from Netanyahu urging that Washington must now set clear red lines for Iran, beyond which military action would be taken.

Relations between the men are strained. Netanyahu's office said Obama had declined a request to meet this week, but the two leaders were expected to speak by telephone.