Taliban militants have attacked a US base in eastern Afghanistan, sparking a lengthy gun battle in which three insurgents were killed.
Reports say the attack on Torkham base in Nangarhar province unfolded after militants torched Nato supply trucks on the highway leading to the base.
Officials said that no Afghan or US soldiers died in the raid. The attackers did not enter the base.
But officials say the financial cost of the attack is likely to be immense.
Many Nato supply vehicles on the road to the base were left badly burned on the highway. Officials closed the Jalalabad-Torkham road - a key route for these vehicles - after the attack.
A Taliban spokesman told the BBC that the group was behind the raid.
Isaf said the attack was unsuccessful: "Our initial assessment of this morning's events, which occurred in the vicinity of a forward operating base located in Nangarhar province, is that it was an attempted but unsuccessful co-ordinated attack by enemy forces."
The base is home to some of the 66,000 US troops serving in Afghanistan along with forces from other countries. Officials say the base was also an important stopping point for Nato vehicles.
There has recently been a spate of attacks across the country, claiming dozens of lives - most of them civilians.
The violence is being interpreted by some as an attempt by the Taliban to assert their presence and test the strength of Afghan forces ahead of the planned withdrawal of US-led forces at the end of next year, the BBC's Karen Allen in Kabul reports.