Egypt says it will not ratify a key treaty banning nuclear tests unless Israel first signs a separate agreement calling for a halt to the spread of atomic bombs. In Cairo on Saturday, Foreign Minister Ahmed Aboul Gheit linked Egyptian ratification of the Comprehensive Nuclear Test Ban Treaty to Israeli acceptance of the Nuclear Non-Proliferation treaty, or NPT. Mr. Gheit said the refusal of Israel to sign the non-proliferation accord is a threat to the stability of the entire Middle East. All Middle Eastern countries except Israel have signed the NPT, which aims to stop the spread of nuclear weapons. Israel and Egypt have both signed the other treaty banning nuclear tests, but neither nation has ratified it. Israel has not officially stated that it has nuclear weapons, but it is widely believed to have about 200 nuclear warheads.