WASHINGTON – The top U.S. commander in Iraq said Monday that the planned withdrawal of all U.S. combat forces by the end of August could be delayed if conditions worsen in the coming months while Iraqis choose a new government.

Army Gen. Ray Odierno said his staff had drawn up contingency plans for a delayed withdrawal that he shared with Pentagon leaders and other U.S. officials during a visit to Washington over the past week. He said he was prepared to make the changes ”if we run into problems,” but he was optimistic that would not be necessary.

Shortly after taking office last year, President Obama pledged to pull out all U.S. combat forces from Iraq by the end of August. Under that plan, about 50,000 troops will remain in the country until the end of 2011 to train Iraqi forces, perform counterterrorism operations and help with civilian projects.

Odierno said U.S. commanders have already reduced their presence in Iraq to about 96,000 military personnel — the first time since the 2003 invasion that fewer than 100,000 U.S. forces have been in the country.

At a news conference at the Pentagon, Odierno said he still expected to carry out the original plan articulated by the White House, but he wanted to be prepared if Iraq experiences fresh instability in the aftermath of national elections scheduled for March 7.

”Right now, our plan is to be at 50,000 by the first of September,” he said. Many Iraqis have said they are worried about a return to widespread sectarian violence as rival factions vie for political control in the midst of the U.S. withdrawal.

Odierno said U.S. forces had not detected a ”significant” rise in sectarian violence in recent months, despite anecdotal reports by Iraqis — particularly minority Sunni Muslims — to the contrary. But he allowed that U.S. military officials were concerned about the possibility leading up to the March 7 elections, as well as afterward, when Iraqi politicians are expected to take weeks to haggle over the makeup of a new government.

”If there’s a problem in forming the government, does it translate into violence?” Odierno said. ”And right now, we’re not sure. We think so far it will probably go fairly smoothly, but we’ll wait to see.”