Despite Olmert admitting that Israel is a nuclear weapons state, the government of Israel thinks it can remain ambiguous, even when the cat is out of the bag. And the US will play along with the delusion. Israel's government doesn't like the NPT. It places limits on who can proliferate and to whom. It will be a huge waste of time to try and bring the Israeli government into it without 100s of "except Israel" clauses that other signatories won't agree to.
UN: Gaza could be 'uninhabitable' by 2020 if trends continue (AP)
from the article: UN nuclear watchdog seeks to persuade Israel to join NPT