Washington, D.C. ? U.S. airstrikes into Pakistan that may have accidentally killed allied fighters have upset the already fragile relations between Washington and Islamabad over how to stem violence in the lawless border region.

Defense Department press secretary Geoff Morrell defended the bombing Wednesday and said it was too early to know whether the strike killed 11 Pakistani paramilitary forces, as alleged by the Pakistani Army.

“Every indication we have is that this was a legitimate strike against forces that had attacked members of the coalition,” he told a Pentagon press conference.

Other U.S. officials said earlier Wednesday that three aircraft launched about a dozen bombs into Pakistan after militants attacked coalition forces in a wooded area near a checkpoint. Conflicting reports about the Tuesday clash were being sorted out by the U.S. military.