The Pentagon has said that it is in talks with the Pakistani officials to resolve the issue of blocking of NATO and US supply line to Afghanistan, but noted that they have developed alternate routes and this was not an immediate national security issue.
There is no immediate impact from the Pakistani move, Pentagon spokesman Col David Lapan told reporters.
"Right now, (it's) too soon to tell because, obviously, we don't know how long that might last. We are in discussions with the Pakistani government in the hope that we can resolve the issue through discussion," Lapan said.
Other crossing along the Pakistan-Afghanistan border remains open to NATO trucks, he said, adding they also have air routes and a northern land route to keep supplies flowing.
About half of the cargo needed by US troops in Afghanistan flows through the two Pakistan border crossings.
Pakistan yesterday closed the Khyber Pass supply route for US-led NATO troops in Afghanistan after a coalition helicopter attack killed three Pakistani soldiers at a border post.
Lapan, however, said that it was the Pakistani border troops that fired first at the US helicopters and the fire was returned in self-defence.
"Even the statement that the Pakistanis put out indicated that their forces used rifle fire at the helicopters as a warning. And, well, if you fire at a helicopter in a combat zone, they'll usually take that as hostile and return fire," Lapan said.
State Department spokesman P J Crowley said ISAF is working with the Pakistani Government to investigate the incident.
"There has been an incident along the Afghan-Pakistan border. We take seriously our responsibilities as a partner, and there's a review ongoing and we are working with the Pakistani Government on both of these issues," he said.