Tension is growing between the United States and Pakistan following a weekend assault by NATO that killed at least 24 Pakistani soldiers.
In response to the incident, Pakistan closed two border crossings used by America's military to supply troops in neighboring Afghanistan.
Pakistan also gave the U.S. two weeks to vacate an air base sometimes used to service CIA drones.
The renewed tension comes after U.S. Special Forces and Afghan commandoes were set to raid a Taliban camp along the border this weekend.
The troops came under fire and NATO forces fired back, fostering a full-blown diplomatic crisis.
"The commander of ISAF has made this his highest priority and has personally ordered a detailed investigation into the case," NATO Brig.-Gen. Cartsen Jacobsen said, The Associated Press reported.
Former Pakistan analyst Marvin Weinbaum said he believes U.S., Pakistani relations have "hit a new low."
"It appears now to be as close as we have seen to a real break in relations," Weinbaum said.
Following the assassination of Osama bin Laden on Pakistani soil last May, the relationship between the two countries were strained.