The Nato airstrikes that killed and wounded dozens of Pakistani soldiers on Saturday were "unintended", alliance chief Anders Fogh Rasmussen said on Sunday.
A total of 24 Pakistani soldiers were killed and 13 others injured when Nato fighter jets and helicopters bombed two border posts in Mohmand tribal region near the Afghan border early Saturday morning.
"This was a tragic unintended incident. I fully support the ISAF (International Security Assistance Force) investigation which is currently underway. We will determine what happened, and draw the right lessons," Xinhua quoted Rasmussen as saying in a statement.
Rasmussen said following "the regrettable incident", he had written to Pakistani Prime Minister Yousuf Raza Gilani to say that the deaths of Pakistani personnel were "as unacceptable and deplorable as the deaths of Afghan and international personnel".
He stressed that the joint interest of Nato and Pakistan was "in the fight against cross-border terrorism and in ensuring that Afghanistan does not once again become a safe haven for terrorists".
"Nato remains strongly committed to work with Pakistan to improve cooperation to avoid such tragedies in the future...Nato and Pakistan share a common goal: a stable Afghanistan in a peaceful region," he said.
Earlier in the day, Pakistani foreign minister Hina Rabbani Khar spoke to US Secretary of State Hillary Clinton and conveyed the "deep sense of rage" felt across the country after the Nato attack.
As per Pakistan's foreign ministry, Khar rang up Clinton in the early hours of Sunday to inform the US government of the decisions taken by the Defence Coordination Committee which met in Islamabad on Saturday evening.
The meeting asked the US to vacate the Shamsi air base in Pakistan. It also decided to block supplies for Nato troops in Afghanistan via Pakistan.