Quoteth the New York Times:
Vice President Joseph R. Biden Jr. told Iraqi leaders on Friday that he and President Obama were committed to helping them resolve their political differences, but he warned that the United States would be unlikely to remain engaged in Iraq if the country reverted to sectarian violence, American officials said.
First of all, I doubt this is true. Even if the American public would not tolerate another over internvetion in the case of possible secession, I have no doubt that the Obama administration would pick sides and try to throw money and guns at whoever is promising to keep Iraq whole.
But besides that – what kind of message does Joe Biden think he's sending, exactly? I assume he intended it towards Malaki and his parochial interests, but it sounds like something that would please the Sunnis and Kurds (and even Malaki's rivals among the Shiites, like Ayad Alawai).
The reason I think that Joe Biden's promise of nonintervention is hollow is that the secession of the Kurds – who would likely be the first to split if the US declared a hands-off approach – would greatly offend US ally Turkey, which is doing everything it can to keep hold on to its own restive Kurdish region. The US would lose a rare friend in the Middle East, and Europe might lose the opportunity to break Russia's monopoly on transiting natural gas from the Caspian Sea with the Nabucco pipeline (though admittedly the Russians have already all but killed the deal).
I imagine that the inspiration for Joe Biden's remarks are his own personal convictions – back in 2006, when he was on the Senate Foreign Relations Committee, his play for Iraq was to split it up into three autonomous regions loosely bound into one nation. That was probably the most intelligent thing I'd ever heard Biden say, though I wish he'd gone further and called for three totally independent states, Turkey be damned.