Addressing Pentagon reporters by teleconference from Afghanistan, Lt. Gen. Curtis Scaparrotti, commander of NATO's International Security Assistance Force Joint Command, spoke of the need to interdict fighters crossing into Afghanistan from Pakistan.
Referring to Afghanistan's Paktika Province, near the border with Pakistan, Scaparotti said there had been indications firing had originated from positions in close proximity to some Pakistan outposts, CNN reported.
"And we immediately get in contact with our Pakistan counterparts in that case. I think the collaboration is at least in some cases local collaborations with the insurgents, and we talk very bluntly with our Pakistan counterparts about this," Scaparrotti was quoted as saying, adding the discussions with the Pakistanis have helped recently.
Referring to recent operations in eastern Afghanistan against the Taliban-linked Haqqani network, which is seen as using its Pakistani havens to attack U.S. troops in Afghanistan, Scaparrotti said the United States believes 200 network operatives may have been captured or killed.
The United States has been pressing Pakistani to go after the Haqqanis but Pakistan has said its military is not ready to do that.
The Wall Street Journal quoted Scaparrotti as saying safe haven for militants in Pakistan is the main obstacle to ending insurgency in Afghanistan.
U.S. officials have spoken lately about the ties between the Pakistani intelligence agency and the militant groups such as the Haqqanis. Pakistan has denied any such relationship.
Scaparrotti said U.S. troops would require "a strong, capable, layered defense" with Afghan security forces to interdict fighters crossing into Afghanistan from Pakistan, said a report on the Defense Department Web site.