Under intense pressure from the United States, the Israeli Prime Minister, Benjamin Netanyahu, gave his blessing to the establishment of a United Nations committee to draft the treaty.
Israel was the last of 61 actual or potential nuclear powers whose assent was necessary. Pakistan complied last week.
Washington is promoting the treaty to head off a nuclear arms race triggered by the Indian and Pakistani tests earlier this year.
Mr Netanyahu came into line after a personal appeal from President Bill Clinton, but specified that Israel was not committing itself to signing the treaty - or to opening its research facilities at Dimona, in the Negev desert, to international inspection.
In a statement to his Cabinet yesterday, the Prime Minister said: "We made it clear to the United States that Israel has its own considerations ... In light of this, we will need clarifications from the US. We also made it clear that we have fundamental problems with the treaty, which we will also discuss with the US."
Israel's nuclear programme was launched in the late Fifties with French co-operation. American analysts believe Israel has stockpiled up to 200 nuclear weapons, with Jericho-2 long-range missiles capable of delivering them anywhere in the Middle East. It is also reported to be testing seaborne missiles to ensure a second-strike option in case of surprise attack.
The Indian and Pakistani tests reinforced Israel's preference for keeping its bomb in the basement. It has never conducted a confirmed test, and official spokesmen do not admit Israel has the bomb.
They do not want to provoke their Arab or Iranian neighbours into testing weapons of their own, as Pakistan did after the Indian explosion.
The deterrent was seen as more vital than ever after the test flight last month of Iran's Shihab-3 missile, capable of striking Israeli targets with non-conventional warheads.Reuse content