So we won’t be getting an Obama-esque 16-month timetable after all. We’ll be getting an … 18-month time horizon. Nuance.

A U.S. official in Washington acknowledges progress has been made on the timelines for a U.S. departure but offered no firm date. Another U.S. official strongly suggested the 2010 date may be too ambitious…

One of the U.S. officials said Secretary of State Condoleezza Rice and Prime Minister Nouri al-Maliki had a long and “very difficult” telephone conversation Wednesday in which she pressed the Iraqi leader for more flexibility, particularly on immunity.

Residual forces will supposedly be out by 2013, the same year McCain targeted for final withdrawal in his Iraq speech a few months ago (doubtless because it would mark the very end of his first term). A lieutenant colonel in the Iraqi Army told the NYT earlier this week that they’d need U.S. troop support until 2015; another officer who didn’t hazard an estimate simply said that without American combat troops Iraq will be “a big disaster.” Bush will, of course, emphasize that the time frame here is conditions-based (presumably with Obama’s approval), but expectations have a momentum all their own. Barring a severe deterioration in security, public pressure on the Iraqi government to enforce the timetable now that they’ve committed to it will be intense, if for no other reason than that Sadr is already making a stink about it and will demagogue it to gain leverage over them if they fail to follow through. Likely result: The IA will be pressed into a lead role before they’re ready and some of those “residual” U.S. troops will find themselves drafted back into a combat/peacekeeper role. That’s probably the most politically palatable solution for all sides, since it would maintain the all-important reduction in absolute numbers while allowing for a more vigorous presence below the radar than the timetable imagines.

I’m mighty curious to see what this does to McCain’s lead on this issue. Exit question recommendation: Read the Times’s piece this morning on the 500th combat death in Afghanistan, formally signaling the transition of the media’s “grim milestone” meme from Iraq to a theater where anti-war sentiment might still accomplish something.