U.S. commanders in Iraq are increasingly convinced that heightened troop levels, announced by President Bush in January, will need to last into the spring of 2008. The military has said it would assess in September how well its counterinsurgency strategy, intended to pacify Baghdad and other parts of Iraq, is working.

"The surge needs to go through the beginning of next year for sure," said Lt. Gen. Raymond T. Odierno, the day-to-day commander for U.S. military operations in Iraq. The new requirement of up to 15-month tours for active-duty soldiers will allow the troop increase to last until spring, said Odierno, who favors keeping experienced forces in place for now.

"What I am trying to do is to get until April so we can decide whether to keep it going or not," he said in an interview in Baghdad last week. "Are we making progress? If we're not making any progress, we need to change our strategy. If we're making progress, then we need to make a decision on whether we continue to surge."

Pentagon spokesman Bryan Whitman said yesterday's announcement of the upcoming deployments "is not a reflection on any decision with respect to the duration of the surge."

As the initial U.S. troop buildup in Baghdad nears its June completion, Odierno and other commanders offered details of how they will execute the military's new Iraq strategy, how they expect insurgents and militias to react, and political factors that will bear upon their success.

Commanders said that even with the ongoing increase in Iraq of tens of thousands of American troops, violence could increase in coming months, and some indicators in Baghdad suggest that is already happening.

Partial data on attacks gathered from five U.S. brigades operating in Baghdad showed that total attacks since the new strategy began in February were either steady or increasing. In some cases, certain kinds of attacks dipped as the U.S. troop increase began, only to begin rising again in recent weeks. Overall, "the number of attacks has stayed relatively constant" in Baghdad, said one U.S. officer, who spoke on condition of anonymity because he was not authorized to be quoted by name.

The U.S. military commands that oversee Baghdad and Iraq as a whole have so far failed to meet requests to release current statistics on attack trends, with some U.S. officers voicing concern that the information would be skewed by critics to argue that the strategy is not working.

Although the military can help curtail violence, U.S. commanders say, Iraqi leaders must ultimately forge political compromises in order to create an enduring peace. "They have to pass a certain amount of key legislation for all of this to move forward. If they don't, we could secure all we want but it's not going to be successful," Odierno said, adding that "the jury's still out" on whether Iraq's leaders will act in the national interest.

The main thrust of the military effort in the near term, Odierno said, is to position a critical mass of U.S. and Iraqi troops inside Baghdad to quell the violence that was spiraling out of control late last year. As currently planned, Baghdad will have 25 battalions of U.S. troops and 38 battalions of Iraqi soldiers and police when the increase is complete, he said.

The push to expand the U.S. and Iraqi presence in Baghdad's neighborhoods reflects what U.S. commanders now acknowledge was a mistaken drawdown in 2005 and 2006 of American troops in the capital, leaving Iraqi forces in their place.