WASHINGTON  When he ordered 30,000 additional troops to Afghanistan last December, President Obama stressed that they would not stay forever. “After 18 months,” he said, “our troops will begin to come home.”

Last weekend, though, he scorned the “obsession around this whole issue of when do we leave,” saying he was focused on making sure the troops were successful. The July 2011 deadline he set was intended to “begin a process of transition,” he said, but “that doesn’t mean we suddenly turn off the lights and let the door close behind us.”

As he hands command of the war to Gen. David H. Petraeus, Mr. Obama is trying to define what his timeline means  but not too much. Even as developments in Afghanistan have made meeting the deadline all the more daunting, Mr. Obama has sent multiple signals to multiple audiences, sticking by his commitment to begin pulling out while insisting that it does not mean simply walking away.

But if he is maintaining maximum flexibility with deliberate ambiguity, the conflicting emphasis has left many wondering just what will happen next summer. The question dominated General Petraeus’s last appearance on Capitol Hill two weeks ago when he testified as head of the United States Central Command overseeing the region. And it may flavor his return on Tuesday to the Senate Armed Services Committee as it moves to confirm his new assignment as commander of coalition forces in Afghanistan.