The Obama administration has said that it respects Pakistan's sovereignty but ruled out any apology to Islamabad at this point of time as the probe into the last week's Nato air strike that killed 24 Pakistani soldiers is yet to complete. "We need to find what happened. We need to get the truth here. We have endeavored to do so through this investigation," state department spokesman Mark Toner told reporters when asked why the US is not tendering an apology to Pakistan over the Nato bombing last week. Toner also reiterated US' commitment to have a strong relationship with Pakistan. US views this as a tragedy for the Pakistani people, he said, adding the US has expressed its sympathies and condolences to them. Secretary of state Hillary Clinton was among the first to reach out to her Pakistani counterpart on the wee hours of the day of incident, he pointed out. "It speaks to how seriously we take this incident that we immediately launched, via CENTCOM, an investigation that's looking into all the causes that surround this event. It is not only important that we find out what happened and why it happened, but we need to really get the details because we need to make sure that we prevent this from ever happening again," he said. Even as Pakistan has made clear that it would not attend the Bonn conference on Afghanistan in protest against the air strikes, Toner hoped Islamabad would have its presence at the meeting which is being attended by some 85 countries and 15 international organisations. "We think it would be regrettable if Pakistan were not to attend this conference. We think it's important for the region, it's important for the neighborhood. It's important that we all work to put Afghanistan on a square and solid footing," he said, adding US Ambassador to Pakistan is engaged in a series of conversations with the Pakistani leaders in this regard. US wants them to be there, he said adding Pakistan's participation in the Bonn conference is valuable. "They're absolutely critical to Afghanistan's long-term stability. But we are also going to find a way to keep them involved in the process moving forward," he noted. "We have continued to talk to our Pakistani counterparts, and our message has been very clear. First of all, we respect Pakistan's sovereignty. Secondly, we are committed to this relationship and making it work. As we've said before, we face many shared challenges from extremists, and we need to tackle them together. This is a relationship that's in both of our national interests, and well as in the interests of Afghanistan, obviously," Toner said. "Then finally we have launched an investigation, an ongoing investigation, albeit at its early stages, that will hopefully find the answers to what happened," the US official said.