The Kyl-Lieberman amendment is, I believe, the first step towards starting a war with Iran. It would be a way to start a war without Congressional approval. It would be a way to start a war without Congressional debate. It is, to use Senator Jim Webb's phrase, "Dick Cheney's fondest pipe dream".
Jim Webb's Senate commentary
"Surely", you sez, "the democratically controlled Senate and House will not allow such a back-door war to proceed!"
"Surely", you sez, "the Congress won't fall for the same song and dance that got us into Iraq!"
"Surely?", I sez, "Like, not!"