The UN will only speak out when/if Muslims are killed in an Israeli retaliatory strike against an Islamic led attack on Israel. If it comes to it, expect Israel to destroy the Aswan Dam and flood Egypt back to the Biblical period. If the Islamicists want war it will eventually come to pass.
I think the Egyptians are smart enough to float the idea that an attack on the dam is the equivalent of a nuclear attack. The media will pick up the story and the Israelis will not be able to do it.