Troops loyal to Ismail Khan have been battling the forces of Pashtun commander Aman Allah Khan for the past four days. At least 60 people were killed in clashes over the weekend, officials said.
Aman Allah's forces captured and briefly controlled Adraskan district about 85km south of Herat city on Tuesday, but lost control of the district in the afternoon after bloody clashes.
"Between 2.30 and 3pm (1030 GMT) Ismail Khan's troops re-attacked and took Adraskan from Aman Allah's troops. There is still some scattered fighting around the district," Defence Ministry spokesman General Muhammad Zahir Azimi said.
The US-led military force said troops from Kabul were ready to be used if fighting spiralled out of control.
"The Afghan government naturally has the lead in this matter and is trying to resolve the situation peacefully," US military spokesman Major Rick Peat said.
Residents have been fleeing as US
jets bomb Aman Allah's forces
"However, they have positioned forces in the area, and are reinforcing them, to use should peaceful means fail."
On Tuesday evening, US warplanes bombed positions held by Aman Allah's forces, Aljazeera's correspondent in Afghanistan Mazin Aman Allah said.
Although, there was some dispute as to whether US warplanes were actually engaged in the tribal conflict, Hamid Almi, the Afghan government's spokesman confirmed the bombing run, saying any attack on pro-government forces in Herat was equal to an attack on the Kabul government itself.
Residents had earlier started to flee the city saying they feared an air strike from US forces would endanger families in their homes.
Ismail Khan was seen distributing weapons to civilians at police and intelligence headquarters.
Uniformed and plain-clothes armed men were seen stationed at every major intersection on Herat's streets.
Soldiers from the Afghan National Army, part of a contingent of 1500 dispatched from Kabul on Sunday and Monday, have secured Shindand airport where fighting broke out early on Saturday.
The latest offensive caps a string of factional clashes among tribal leaders battling for control of the western provinces of Herat, Farah, Badghis and Ghor in recent months.
Ismail Khan has posted armed
men around the city of Herat
Ismail Khan has ruled Herat city with an iron fist, and is accused of cracking down hard on his opponents.
He has also been at loggerheads with Kabul over his reluctance to remit taxes on an estimated monthly income of up to $9 million to the cash-strapped central government.
These clashes highlight Afghanistan's security situation after the US invaded it and appointed an interim government following the 11 September 2001 attacks in the US.
As the Afghanis prepare for presidential elections in October, analysts say Afghanistan is not ready, but is being used for Bush's own election year political point-scoring in the wake of what the US is facing in Iraq.