According to a New York Times report, Obama, reacting to General Petraeus's demand for "maximum flexibility" in setting withdrawal schedules, said he "pushed back" when he met with the commander in July by making the case for sending more forces to Afghanistan, which the Democratic candidate views as the main battleground against terrorists. McCain, who argued that a favorable outcome in Iraq is vital for American strategy in the Middle East and its overall efforts against terrorists, repeatedly invoked General Petraeus's counter-insurgency strategy and said he would be inclined to give General Petraeus considerable latitude in setting force levels in Iraq.
At the heart of the dispute is Obama's 16-month schedule for withdrawing American combat brigades, a timetable that is about twice as fast as that provided for in a draft American and Iraqi accord.
"The danger with Obama's rigid timetable is that it may not allow U.S. commanders to react to events on the ground," said Toby Dodge, a specialist on Iraq at the University of London and a former adviser to General Petraeus.
"McCain's policies lack the detail needed to confront the challenges of politics in Iraq. Policies developed to please the party faithful are not being subjected to close electoral scrutiny and do not match the complex political and military realties of Iraq," he adds.
There is no question that the American reinforcements dispatched by President Bush have helped reduce sectarian violence, both directly through military operations and indirectly by helping encourage the spread of the Awakening movements, in which neighborhood watch groups have taken on Sunni extremists.
But American commanders have also warned that the situation remains fragile, and that there has been mixed or no political progress in other areas. For the candidate who is elected, the challenge is how to sustain the reduction in violence and encourage political headway now that the "surge" of combat brigades is over and the military is scheduled to withdraw yet another brigade by February.
On the surface, the two candidates' views on troop cuts appear to have converged: each candidate envisions reductions in American force over his first term, as does the Iraqi government. But the similarities vanish upon closer inspection. Obama's views on troop cuts were forged in late 2006 as Iraq appeared to be approaching a full-scale civil war. Drawing on the bipartisan Iraq Study Group report, he opposed Bush's troop reinforcement plan and sponsored legislation in January 2007 that would have removed all American combat brigades by the end of March 2008, while allowing a small force to remain for training, counter-terrorism and the protection of American Embassy and personnel.
At that time, American intelligence agencies warned in a national intelligence estimate that the removal of all American and allied forces within 18 months would "almost certainly" lead to a significant increase in sectarian fighting. Mr. Obama has said he would remove the remaining combat brigades at the rate of one or two a month over a 16-month period. In the interview he argued that it was important to set a new course that would put pressure on the Iraqis to overcome their differences, free up more American forces for Afghanistan and other potential trouble spots, and reduce expenditures so they could finance programs at home.
McCain has argued that reductions should be determined by political and military circumstances, a stance taken by Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff. Providing the American commander in Iraq with maximum leeway, however, could entail some difficult trade-offs.
Asked to clarify his views, Mr. McCain said in the interview that he envisioned "the withdrawal of U.S. troops over time." He said the question of whether there should be a long-term American military presence in Iraq for training or other purposes should be resolved in discussions with the Iraqis, and cited Kuwait as a possible model.
At its most basic, the dispute between Mr. Obama and Mr. McCain centers on the importance of the American mission. For Obama, the invasion of Iraq was a mistake and the efforts he would make there are essentially a matter of damage limitation. By defining a series of minimal goals, Obama would seek to reduce American forces.
For McCain, the problems the United States has encountered in Iraq stemmed from what he saw as the many blunders made during the early years of the occupation, errors that he asserts have been largely remedied by the surge of reinforcements and a new counterinsurgency strategy.