The pullout of major U.S. combat units from Afghanistan may not start until the peak fighting season ends in late fall, U.S. military officials said Wednesday, although 800 National Guard soldiers will go home this month.

Details of the U.S. drawdown are still being worked out, but thus far the only major combat unit designated to depart Afghanistan and not be replaced is a Marine infantry battalion set to leave in late fall, officials said. That means the military could retain virtually all its current combat power until the fighting goes into a seasonal lull and still meet President Barack Obama's order to reduce the force by 10,000 by year's end.

It is possible, though unlikely, that new U.S. commanders arriving in Kabul this month will speed up the drawdown.

Speaking to reporters at the Pentagon from his headquarters in Kabul, Army Lt. Gen. David Rodriguez said the full plan for reducing the U.S. force will not be worked out until autumn.

Beyond the 10,000 troops this year, a further 23,000 troops are to be brought out by September 2012.

There currently are about 100,000 U.S. troops in Afghanistan as part of an international coalition.

Rodriquez, the second-in-command in Kabul, said the 3rd Battalion, 4th Marine Regiment, from Twentynine Palms, Calif., would return home by September. Later, his staff said he had misspoken. Officials who spoke on condition of anonymity in order to discuss sensitive details said the Marines would leave in late fall.

The battalion has about 800 Marines in Helmand province, a heavily-contested area in the heartland of the Taliban insurgency. The province's capital of Lashkar Gah is one of several areas that are being transitioned this month to Afghan control, beginning a process intended to have the entire country under Afghan control by the end of 2014. At that point, all U.S. and other foreign combat forces are to have been withdrawn.

Rodriguez, who has spent more than 40 months in Afghanistan over the past 4 1/2 years, said he believes the Obama pullout plan for 2011 and 2012 can be carried out without undue risk to the military's mission of gradually handing over security responsibility to the Afghans. The troop withdrawal plan has been criticized by some Republicans as too fast and risky, while some Democrats have complained that it is too slow and cautious.

"The decision's been made and now it's our turn to execute the decision," Rodriguez said. "And we can do that without a significant change in risk that puts any of the mission at risk at this point in time."

When he announced June 22 that all 33,000 reinforcements he had sent to Afghanistan last year would be brought home, Obama said the pullout would begin in July but he left it to his commanders to decide the details. That has given commanders flexibility in figuring out which units to send home and on what schedule.

Rodriguez said it will begin with the departure this month of two Army cavalry squadrons: the Nebraska Army National Guard's 1st Squadron, 134th Cavalry Regiment, from Lincoln, and the Iowa Army National Guard's 1st Squadron, 113th Cavalry Regiment, from Sioux City.

The 1-134th has about 300 soldiers in Kabul and the 1-113th has about 500 in Parwan province north of Kabul.

Rodriguez himself is finishing his tour this month and will be replaced next week by Army Lt. Gen. Curtis Scaparrotti.

In his final scheduled news conference before returning to the U.S., Rodriguez said violence levels in Afghanistan are up slightly over last year, and he doubted it would go down until 2012. And he said the international military coalition plans to shift its main counterinsurgency focus from the south of the country to the east, where violence has been on the rise. He said the timing of that shift is yet to be determined.


Robert Burns can be reached at http://twitter.com/robertburnsAP