PRESIDENT Barack Obama faces split opinions within the military on whether to make the speedy withdrawal from Iraq he championed on the campaign trail. Obama's top generals in Baghdad are pressing for an elongated timetable, while some influential senior advisers inside the Pentagon are more amenable to a quicker pullout. Although Obama has yet to decide the matter, his announcement last week that he is sending thousands more combat troops to Afghanistan implies a drawdown of at least two brigades from Iraq by summer. That does not answer the question that has been dangling over Iraq since he took office in January: Will Obama stick to his stated goal of a 16-month pullout or opt for a slower, less risky approach? Gen. Ray Odierno, the top American commander in Baghdad, favors a longer timetable for leaving Iraq. He sees 2009 as a pivotal year, with parliamentary elections set to be held in December; he does not want to lose more than two of the 14 combat brigades that are now in Iraq before the end of the year. Also, he believes the US military will need to remain engaged in Iraq, to some degree, for years to come. Odierno's boss at US Central Command, Gen. David Petraeus, leans toward Odierno's view. Gen. David McKiernan, the top US commander in Afghanistan, has steered clear of the debate over withdrawing from Iraq, but he sees his battlefield as an increasingly urgent priority, not just for additional combat troops but also for Iraq-focused surveillance aircraft and more civilian support. There are now about 146,000 US troops in Iraq, compared with 38,000 in Afghanistan. Obama has directed 17,000 more to head to Afghanistan, including Marines and soldiers who had been in line for Iraq duty. At the Pentagon, a more mixed view prevails. The uniformed service chiefs see Iraq as a strain on their troops and, more broadly, a drain on their resources. The Marines, in particular, are in the tough position of having a foothold in both major US wars, Iraq and Afghanistan. As a relatively small service, the Marines would prefer to concentrate more fully on Afghanistan, if only they could get out of Iraq. Neither Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, nor Defense Secretary Robert Gates has said publicly whether he supports a 16-month withdrawal timeline. But they have their own perspective: an obligation to consider the full spectrum of threats and potential threats to US national security. “There's a very clear understanding of what is at stake here,” Mullen said Feb. 10. “And it's very natural for Gen. Odierno to want to go slower and to hang onto capability as long as possible,” he added. “That's not unusual. It's very natural for Gen. McKiernan to say, ‘I need more.' And so that's the tension. We don't have an infinite pot (of resources and deployable forces). We have to make hard decisions about where to accept risk.” In internal discussions, the emphasis appears to be on getting out responsibly rather than quickly, several officials said, speaking on condition of anonymity because no decisions have been made. Obama must weigh an array of hard-to-figure trade-offs in security and politics. And he must reconcile his conviction that the combat phase of US involvement in Iraq must end with his commanders' concern in Baghdad that hard-fought gains could be squandered. It boils down to this: How much more effort is the Iraq war worth? What is the risk of leaving too soon? Is the 16-month timetable too short, given the uncertain state of stability and political reconciliation in Iraq and the potential cost of seeing the country slide back into widespread sectarian war? And is anything substantially beyond 16 months too long, given the call for still more troops in Afghanistan, where Obama himself has said the battle against extremists is going in the wrong direction? Obama still is considering his options, which officials say include a less hurried, 23-month withdrawal. One clue to some of the thinking inside the White House might lie with the views of Obama's national security adviser, retired Marine Gen. James Jones. Jones co-chaired a study published in January 2008 on the way ahead in Afghanistan. The group endorsed the idea of providing more military support for Afghanistan, including resources that become available as combat forces are withdrawn from Iraq. The president has an additional factor to weigh: the political cost of backing off the 16-month pullout timetable that was a prominent feature of his campaign. Although he has said he thinks 16 months is a reasonable timetable, he also has assured military leaders that he will consider their advice.