The Pentagon will send nearly 4,000 additional troops to Afghanistan in an effort to turn around a war that commanders have described as a stalemate. Earlier this week, US President Trump provided his defence secretary, Jim Mattis, with the authority to determine troop levels in Afghanistan. The Pentagon is reviewing the strategy for Afghanistan, which Mattis said may take several weeks. But the question of sending additional troops is considered urgent in order to halt recent Taliban advances as another fighting season gets under way. The Taliban generally steps up violence in the warm months. The top commander in Afghanistan, General John Nicholson, has said a few thousand additional troops would be required to turn the tide on militants. “We are not winning in Afghanistan right now,” Mattis told Congress this week. Marine General Joe Dunford, chairman of the Joint Chiefs of Staff, said last month that it if the US and Nato countries decide to increase forces they should be prepared to do so quickly. There are about 8,400 US troops in Afghanistan now in addition to several thousand troops from allied countries. Nato forces are also expected to increase troop levels in Afghanistan. The Pentagon has said that any troop increase would not change the mission of the forces there. Afghan security forces are leading the fight and US and Nato troops are serving as advisers and providing air and other critical support. The additional troops will allow the US-led coalition to provide more advisers to Afghan combat units. The US had as many as 100,000 troops in Afghanistan in 2010 and 2011, but in 2013 turned over the primary responsibility for the war to Afghan forces. In recent years security in the country declined as the US decreased its presence.