Neighbors Syria, Iraq and Iran are signatories to the nuclear non-proliferation treaty, but Israel is not. The only other nuclear nations that haven't signed on are Pakistan, India and North Korea. That means inspectors from the International Atomic Energy Agency (IAEA) are not allowed to visit Israel to determine whether nuclear material is entering or exiting the country, or any other aspects of weapons development. The only exception is for a small research reactor.
IAEA officials in Vienna refused to comment about any aspect of Israel's nuclear weapons program.
But according to Kristensen, the U.S. intelligence community estimates that Israel has 80 to 90 nuclear warheads. Israel has the capability of launching these warheads via ballistic missiles (called the Jericho 2) that have a range of about 1,500 kilometers, or 930 miles, on missiles on U.S. supplied F-15s and F-16 fighter jets and on Cruise missiles aboard diesel-powered submarines supplied by Germany.
Why the secrecy? Kristensen and other experts say the program has been kept quiet since Israel began it in the late 1950s. Documents from the Nixon Administration declassified in 2006 revealed that President Richard Nixon agreed to allow Israel's leader Golda Meier to continue developing nuclear weapons as long as Israel didn't acknowledge it or conduct public weapons tests, according to Avner Cohen, senior fellow at the Monterey Institute for International Studies and author of several books on Israel's nuclear program.