Washington: The US said it is concerned about its relationship with Pakistan in the aftermath of the weekend's cross border fire by NATO that killed 24 Pakistani soldiers, but stressed that it is in the best interest of both the countries to maintain relationship.

"We're concerned about the impact of this incident on our relations with Pakistan," State Department spokesman Mark Toner told at his daily news conference when asked about the statements coming out of Islamabad that the US can't take Pakistan for granted and it is not going to be business as usual with the United States.

Toner said Secretary of State Hillary Clinton and the Defence Secretary Leon Panetta have been in communication with leaders of Pakistan in this regard.

"You know, we're trying to work through this. There's an investigation under way. We certainly recognise that our cooperation with Pakistan, as we've said many times, has yielded very tangible progress and tangible results, and so we want to see that continue," he said.

Besides the investigation by NATO-led International Security Assistance Force (ISAF), the US Central Command is also leading an investigation into the incident that has plunged US-Pak relationship into a deep crisis.

"There is an investigation under way that's looking into what exactly transpired," he said.

"We have long said when there have been incidents in this relationship, challenges in this relationship, that we're going to work through the challenges because this relationship is vitally important to both our countries. We both face a shared threat from extremists," Toner said adding that the US is committed to working through these kinds of challenges because they need to make progress and it has to continue.

The State Department spokesman hoped that Pakistan will attend the upcoming Bonn conference on Afghanistan, which Islamabad has reportedly has said that it will not attend in protest against the weekend s incident.

"We hope that they do in fact attend this conference because this is a conference that is about Afghanistan and building a more stable and prosperous and peaceful Afghanistan," Toner said adding that there is no decision on postponing the event.

"We believe it's very much in Pakistan's interest to attend the Bonn conference because, the focus of that is all about trying to build a more stable and peaceful Afghanistan," he said.

"This is a relationship that's weathered difficult times and has yielded success in our shared battle against terrorists and extremists. We are clear-eyed about where we're at in the relationship. I think we're committed to working through it," Toner said.