KABUL - US Deputy Secretary of State Richard Armitage reassured Afghan leaders that Washington was committed to the war-torn nation even as attention was focused on Iraq. "President Bush has asked me to come to Afghanistan ... to dramatically make the point that the United States, although we may at present be occupied by Iraq, is not going to forget our responsibilities in Afghanistan and that we are able to do two things at the same time," Armitage told reporters at a press conference in the ruined Kabul museum. Shortly after Armitage spoke, a mysterious explosion shook Kabul which left the deputy secretary of state unfazed and was later identified by a US military spokesman as the sonic boom of a passing aircraft. Armitage said US troops would remain in Afghanistan until the country was secure. "The United States will withdraw forces once we're sure that the government of Afghanistan feels perfectly secure and the people of Afghanistan have found necessary stability," he said after a meeting with President Hamid Karzai and Foreign Minister Abdullah Abdullah. A US-led coalition of more than 10,000 troops is currently engaged in hunting down Taliban and al-Qaeda fighters, but is not involved in providing security in the provinces. In a report to the UN Security Council on Tuesday, special UN envoy for Afghanistan Lakhdar Brahimi said attacks by the Taliban, al-Qaeda and Hekmatyar loyalists had increased to an almost daily occurrence. Brahimi also repeated his call for the extension of the peacekeeping International Security Assistance Force beyond its present confines of Kabul. Armitage said the US "took careful note" of Brahimi's statement, but had different views. "We ourselves have slightly different views about the most effective way to bring security, reconstruction, stability to Afghanistan," he said, pointing to a US-led civil-military programme to establish provincial reconstruction teams. Three have been opened and more are due to be set up shortly. "We think this is a very effective way of providing security and extending the reach of the central government," he said. Security in the provinces is a major headache for Karzai. The killing of an Afghan deminer on Saturday prompted the UN to suspend missions in southern Afghanistan. At least four US soldiers, a foreign Red Cross worker and an Italian tourist have been killed since the end of March. Armitage said he had also discussed the situation on the Pakistani border with Karzai and Abdullah. Afghan and US military officials say Taliban and al-Qaeda members cross the border to launch attacks in Afghanistan. "It is a very porous border, the tribal areas are well known for their own independence. I think we all have to do more to make sure that the remnants of the Taliban are got rid of for good," he said. On his visit last week, Rumsfeld announced an end to "major combat operations" in Afghanistan and said the country had moved into the reconstruction and redevelopment stage. "My own view is that in things large and small, the United States and other nations are trying to be a part of the reconstruction and redevelopment of this nation," Armitage said after visiting a US-AID funded water pumping station in Kabul. Armitage said the United States was going to be a "worthy partner" in the economic and social development of Afghanistan.