NATO's supreme commander, John Craddock, is in Afghanistan for talks with officials and troops trying to combat an increasingly violent insurgency.
NATO did not release further details. The American general told the Associated Press Monday that he does not oppose NATO members talking to Iran about using Iranian territory to supply their forces in Afghanistan.
Craddock says NATO is considering alternatives to using routes through Pakistan because of attacks in the country on NATO supply convoys.
Pakistani officials said Tuesday suspected militants blew up a bridge in northwest Pakistan, cutting a key supply route for NATO forces in Afghanistan.
The U.S. Defense Department says NATO forces in Afghanistan reported a 33 percent increase in insurgent attacks across the country in 2008. It was Afghanistan's worst violence since the 2001 U.S.-led invasion that ousted Taliban militants from power.
The Pentagon said Monday the Taliban has evolved into a resilient insurgent force that is challenging the Afghan government for control in the south, east and west of the country. The assessment was part of a regular report to the U.S. Congress.
The Pentagon report says NATO and Afghan forces do not have sufficient resources in the south, allowing the Taliban to retain its hold on the local population.
It also says the Afghan government is one of the weakest in the world. It says Kabul is hampered by pervasive corruption and a lack of sufficient leadership and expertise.
U.S. House Armed Services Committee chairman Ike Skelton expressed disappointment Tuesday with Afghanistan's worsening security situation.
He said U.S. forces in Afghanistan will continue to be short-changed unless the U.S. and its allies provide sufficient military and civilian resources.
Some information for this report was provided by AFP, AP and Reuters.