There are signs of the Taleban leadership "falling apart", a US military spokesman said on Saturday, citing reports this week that a breakaway faction no longer recognises Mullah Mohammad Omar.
The one-eyed Mullah Omar became one of the world's most wanted men for helping shelter Osama bin Laden and his al Qaeda network until late 2001, when US led forces drove the Taleban militia from power in Afghanistan.
Reuters reported on Monday that a dissident group named Taleban Jamiat Jaish-e-Muslimeen (Muslim Army of the Taleban) had broken away, taking with it about one-third of the Taleban's fighting strength.
"That's a significant development which demonstrates the Taleban are falling apart a little bit on the leadership side," Major Scott Nelson told a regular news briefing in Kabul.
Nelson said the military was still assessing what impact the split was having on the Islamist militants' strategy and operations against US-led forces in Afghanistan.
"That fissure is widening - we see that. Specifically what that means we're still looking into it," he said.
The new group was being led by Mulla Syed Mohammad Akbar Aga, a 45-year-old commander from the southern Afghan city of Kandahar, Sabir Momin, who was the Taleban's deputy operations commander in southern Afghanistan, told Reuters on Monday.
The rift within the Taleban comes hard on the heels of a series of arrests of al Qaeda members in neighbouring Pakistan, suggesting success on two fronts in the US-led war on terror.
There are around 18,000 US-led troops combing the south and east of Afghanistan for Taleban and al Qaeda members.
Another eight thousand peacekeepers are part of the NATO-led International Security Assistance Force (ISAF) stationed in Kabul and northern parts of the country.
On Friday, one US soldier was wounded in a Taleban ambush of a convoy in south-eastern Paktika province, and another was hurt when his patrol vehicle was hit by an explosive device in neighbouring Zabul province.
Taleban spokesman Abdul Latif Hakimi told Reuters four fighters had been wounded.
The US military has lost 98 servicemen in Afghanistan since late 2001, the most recent a soldier killed when the Black Hawk helicopter he was travelling in crashed due to a mechanical problem on Thursday. The US military says there was no hostile fire involved in the incident.
The peacekeeping force has been beefed up ahead of Afghanistan's landmark presidential election in October, as the Taleban and its allies are expected to intensify a campaign of violence. Close to one thousand people have been killed in the past year, including militants.
Taleban remnants are believed to have links with al Qaeda, the group they sheltered from the 1990s, and militant Islamic forces loyal to former Afghan prime minister Gulbuddin Hekmatyar.