US Defence Secretary Robert Gates has defended the right of American forces to strike at what he called militants on the Pakistani side of the Afghan border. The US would take "whatever actions necessary" in self-defence, he said when asked if Pakistan had authorised such airstrikes, adding that Washington would prefer for Pakistan to tackle militants itself. Gates, fresh from a visit to Afghanistan, is in London for talks with other Nato defence ministers. Speaking to BBC security correspondent Frank Gardner, Gates welcomed the Pakistani Army's "much more aggressive" approach to militants along the border in recent weeks. He said that the militants were the "common enemy" of Pakistan, Afghanistan, and US troops and their allies. "Our goal is to partner with the Pakistanis and enable them to deal with this threat on the border themselves," he said. Asked whether the Pakistani government had authorised US airstrikes on Pakistani territory, Gates said, "I wouldn't go in that direction." "I would just say that we will take whatever action necessary to protect our troops." The strategy for Afghanistan is a priority for Gen David Petraeus, due to oversee US military operations throughout the Middle East, Afghanistan and Pakistan, as head of Central Command from the end of October. Speaking recently to the BBC, the former US commander in Iraq said he had to turn around the Nato mission in Afghanistan, where the trend was "in the wrong direction". Gates told the BBC that the US tried to keep civilian casualties to a minimum. He accused the Taliban of using them as human shields. The issue has caused increasing anger in Afghanistan. Agencies add: The Bush administration is considering changing its war strategy in Afghanistan in the light of rising levels of violence and an increasingly complex insurgent threat, Defence Secretary Robert Gates said Thursday. "You have an overall approach, an overall strategy, but you adjust it continually based on the circumstances that you find," Gates told a group of reporters at a London hotel on Thursday. "We did that in Iraq. We made a change in strategy in Iraq and we are going to continue to look at the situation in Afghanistan." Pressed for more details about the review of Afghan strategy, Gates would say only, "We're looking at it." He did not reveal whether the White House has launched a formal review of its war strategy. But his remarks indicated that the administration sees a need to make some adjustments as progress there remains slow. Gates mentioned Al-Qaeda and bans of foreign fighters, many of which find refuge in Pakistan and are able to slip across the largely unpoliced border to launch attacks. A senior defence official travelling with Gates said later that the administration was examining a range of strategic questions, including whether to reduce the combat role of Nato troops in Afghanistan in light of planned increases in US combat troops. The official, who spoke on condition of anonymity, said it amounted to a broad review that included more than just military aspects of US strategy. Gates also said that at a Nato meeting here Thursday and Friday he would raise the issue of how to share the cost of a planned doubling in the size of the Afghan national army. He said building up the capacity and effectiveness of Afghanistan's own security forces is 'ultimately the exit strategy for all of us'. Gates noted that violence has been on the rise in Afghanistan for the past two years, in part because of cross-border attacks from Al-Qaeda, Taliban and other extremist elements that find refuge in neighbouring Pakistan. That has made it harder for US and allied troops to improve security, which Gates said has restricted gains in other vital areas such as weeding out government corruption and developing the economy. Violence has been on the rise in eastern and southern Afghanistan, and Gates said it reflects in part an increasingly complex set of insurgent components, beyond the Taliban rebels who had ruled Afghanistan and granted a refuge in the country for Osama bin Laden prior to the terrorist attacks of Sept 11, 2001. "It's not a centrally controlled Taliban insurgency against the government," he said. "It's a number of different challenges against the government." Gates also told reporters that he believes Britain intends to add more troops in Afghanistan, but he offered no numbers and said he was not sure the government here had made a final decision. Any changes in strategy now being contemplated would not be as substantial as Bush's decision in January 2007 to take a fundamentally different approach in Iraq, Pentagon Press Secretary Geoff Morrell said. Bush added more than 21,000 combat troops in Iraq and endorsed an overhaul of military strategy. "Nothing of that magnitude" is being considered for the war in Afghanistan, Morrell cautioned. Gates did not say the current US approach in Afghanistan is failing. Nor did he explicitly call for a change of direction. He alluded, instead, to the 2007 makeover of US strategy in Iraq and suggested in an interview with a group of reporters that the administration is reconsidering fundamental aspects of its strategy. In Washington, military analysts Anthony Cordesman of the Centre for Strategic and International Studies issued a report concluding that the war is "probably being lost at the political and strategic level." "The situation in Afghanistan has been deteriorating for nearly half a decade, and is now reaching a crisis level," Cordesman wrote.