WASHINGTON - US commanders may send an additional 2,500 troops to fend off the Taliban in northern Afghanistan, a region that had been relatively peaceful until recently, a defense official said Friday.

US officers were conferring with German commanders leading Regional Command North about shifting some the forces in a US troop buildup to the north instead of the south, the official told AFP.

The "tentative" plan was for roughly 2,500 American troops, including trainers for Afghan security forces, to deploy to the north, said the official, who spoke on condition of anonymity.

President Barack Obama approved the deployment of 30,000 additional troops in December to turn the war around, and most of the 10,000 that have arrived so far have been sent to the volatile south, the spiritual heartland of the Taliban insurgency.

Plans for a possible shift of forces emerged after a senior German general said the NATO-led force was planning an offensive in the northern Kunduz province.

General Bruno Kasdorf, chief of staff of the NATO-led International Security and Assistance Force, told German ARD public radio Thursday the operation would be "similar" to the offensive currently underway in the southern province of Helmand involving 15,000 US, NATO and Afghan troops.

Compared to the south, violence is still relatively low in the north, but Taliban forces have stepped up attacks in the area in recent months and tried to disrupt vital NATO supply routes from neighboring Uzbekistan that run through Kunduz, officials said.

Another defense official said the Taliban, which has its roots in the Pashtun community, is seeking to expand its reach across the country and tended "to focus on the Pashtun pockets in the north."

But he said the center of gravity in the war, for the insurgents and for NATO-led forces, remained in the south, where US reinforcements have poured in since Obama ordered the surge of American forces.

Germany has around 4,300 troops in Afghanistan, the third-largest contingent after the United States and Britain.

General Stanley McChrystal, the top commander of US and NATO troops in Afghanistan, told reporters this week that German forces in the northern city of Mazar-e-Sharif were concentrating their efforts on Baghlan and Kunduz "as well as a number of other areas across the north."

He said security was better than in the south but that "effective and focused operations" were still required in the area.