KABUL (AFP) - Seven years after the attacks on the World Trade Centre, Afghanistan is again the frontline of the US-led "war on terror" with extremist unrest intensifying and a new focus on Pakistan's tribal areas. Less than two months after the September 11, 2001 attacks, the United States and its allies had ousted the Taliban regime which had refused to hand over Al-Qaeda chief Osama bin Laden. But today Osama bin Laden is still on the run, the Taliban have regrouped - notably in the south and in border tribal areas of Pakistan - while the government in Kabul struggles to assert its authority. The rise of violence in Afghanistan and relative calming of Iraq have opened the way for such reinforcements, and the Pentagon has already spoken of a first deployment of 4,500 soldiers by the end of the year. Admiral Michael Mullen, the most senior US military officer, also warned last month of the growth of the Taliban and attacks that would get "more and more sophisticated", as seen with recent ambushes on foreign soldiers. US forces have increasingly turned their focus on Pakistan's frontier belt, stepping up missile strikes and this month helicopters even dropped ground troops into a village, angering Islamabad. In Afghanistan, which has a long history of resistance to outsiders, international forces are making steady progress but "victory is slow," a US commander in Afghanistan, General Jeffrey Schloesser, acknowledged last week, calling for extra soldiers, warning of a possible "winter offensive" by the Taliban and said the militants were preparing "spectacular attacks". US allies are meanwhile concerned about their own growing casualties, and the difficulty of winning "hearts and minds" as Afghans grow weary of reports of civilians killed in error by military air strikes. Meanwhile, seven years on, Al-Qaeda's catastrophic attacks on the United States go a long way to defining this year's White House race even as Barack Obama and John McCain put on a veneer of unity to commemorate Thursday's anniversary. The Democratic and Republican White House contenders plan to pay their respects together at the site of the fallen World Trade Centre in New York, in a rare truce to their bad-tempered battle for the November 4 election. "I believe that foreign policy may still be the top issue in the race - not because it is automatically the most important, given the state of the economy, but because national security is an area where voters realise the centrality of the role played by the President, and also is the area where McCain and Obama have many of their sharpest differences of opinion," Michael O'Hanlon, a national security expert at Washington's Brookings Institution, told AFP. "And of course, 9/11 is still one of the most important defining images/moments in the American national security debate, and most other key debates can be related to it in one way or another," he said. A week after the attacks, Obama wrote in Chicago's Hyde Park Herald that the immediate focus must lie on strengthened domestic security, improved intelligence and dismantling the extremists' "organizations of destruction." John McCain, from the start, was pugnacious in calling for the United States to go on a war footing against extremism wherever its threat was felt - and that, he said, included Iraq. But while vowing to pursue Al-Qaeda mastermind Osama bin Laden to the "gates of hell," the Arizona senator has decried Obama's demand for US strikes on terror cells inside Pakistan if the Islamabad government is unwilling to act.