Washington  - The United States Wednesday expressed regret over an air raid that killed 11 Pakistani troops and opened a rift between the two countries.

"This is a regrettable incident. We're sad to see the loss of life among the Pakistani military, who are partners in fighting terror," Gonzalo Gallegos, a US State Department spokesman, said.

The United States carried out an airstrike on the Pakistani post near the border with Afghanistan after coalition soldiers came under fire from insurgents, the US military said in a statement.

The coalition aircraft destroyed the paramilitary Frontier Corps post in the Mohmand tribal region used as refuge by Taliban militants.

Gallegos said the incident shows there is a need to improve communication between US-led forces in Afghanistan and Pakistani authorities to ensure similar episodes do not take place in the future.

"This is a reminder that better cross-border communications between forces is vital," Gallegos said.

The mistake sparked outrage from the Pakistani government, which summoned US Ambassador Anne Patterson to the foreign ministry. (dpa)