From an April '06 interview with Sen Kerry on the IWR and Biden-Lugar Amendment:
So if there was no private meeting, no agreement to join with the majority, then why vote for the resolution? "It didn't happen in a vacuum," he said. "I'd been supporting the Biden-Lugar Amendment, a bipartisan effort that would have required that the inspections be completed before any military action took place. We had a good chance of passing it. That amendment reflected my position on the war.
"Then one day we turned on the TV and Joe Lieberman was in the Rose Garden with the President, saying that he was supporting the resolution - as is. We realized that, as of that moment, the amendment was effectively dead."
http://www.huffingtonpost.com/rj-eskow/kerry-calls-to-respond-_b_18844.html?p=2