The United States urged Pakistan on Tuesday to reconsider its decision to boycott a conference on Afghanistan in Germany next week, saying it plays a key role in the future of its war-torn central Asian neighbour. Pakistan decided earlier Tuesday to boycott the December 5 Bonn conference as it widened its protest over lethal cross-border Nato strikes on Saturday that have exacerbated a deep crisis in US ties. "It is important to note that this conference is about Afghanistan, about its future, about building a safer, more prosperous Afghanistan within the region. So it's very much in Pakistan's interest to attend this conference," State Department spokesman Mark Toner told reporters at a news briefing. "Seeing this on a continuum, Pakistan was obviously in Istanbul and pledged support for a strong, prosperous Afghanistan within the region. It was a very important statement, and, again, now we're moving towards Bonn. This is an important opportunity," he noted. It's also worth noting that there's still going to be 85 nations and 15 international organisations that are going to be in Bonn. "So while we would like to have Pakistan there, we still think it'll be a valuable opportunity to talk about Afghanistan's future," Toner said, but refrained to use the word "regret" or "disappointed" on Pakistan's decision, which the State Department spokesman normally reserves for. "I think I said it as plainly as I can. You know, it's in their interest, so we think, you know, it's important that they be there," Toner said when asked if he regrets the Pakistani decision not to come to Bonn. He said the US is conducting an investigation that will look in to the matter. "In every conversation we've had and continue to have with the Pakistani government, while expressing our deep condolences about the incident, we're also pledging to continue to work together,' the US official said. Toner, however, noted that there is no change in US strategy towards Afghanistan in view of the recent decisions taken by Pakistan following the weekend s incident on the Af-Pak border in which some 24 Pak soldiers were killed in a cross-border fire by NATO. "We have had a significant incident that took place, but this has not disrupted our overall strategy vis-a-vis Afghanistan, vis-a-vis Pakistan. We're still committed to working with both countries to build a more stable and secure future for both countries," he said. "Our approach to Afghanistan remains on track. We are still planning on the Bonn conference. It's not going to be delayed or postponed. We still have, as I mentioned, some 85 nations and some 15 international organisations who will attend. We think it's important to go forward with our plans, long-term plan for Afghanistan," he said. "You know, do we want Pakistan to be involved in that future? Yes. Is it vital? Certainly. And we're going to work towards making sure that Pakistan is, indeed, involved as we move forward. Pakistan has been involved in the past, and we believe it will be in the future," Toner asserted. Pakistan, he said face an existential threat in the form of extremists who operate in that border region. "It's a threat to Afghanistan's capital. It's a threat to Pakistan's stability. We need to address it," he said adding that Secretary of State Hillary Clinton during her recent trip to Islamabad discussed the need for Pakistan to address some of these threats head-on. "That threat remains intact. So we need to address it," he said. "It is absolutely vital, as we've seen, and, you know, not just from a security standpoint, but from a political and economic standpoint, that there is closer cooperation between Pakistan and Afghanistan. "It's very much in Pakistan's long-term interests, as it is, in fact, in the long-term interests of every one of Afghanistan's neighbors, that Afghanistan has stability, has prosperity, and is a safe and secure neighbor, with safe and secure borders. "Those are all very much not only in Pakistan's interest, but in all of Afghanistan's neighbours' interests," he said.