KABUL (Reuters) - (This version of the July 23 story corrects reference to A-29 Super Tucano in para 7. The aircraft are built in the United States under an agreement between their Brazilian manufacturer, Embraer and Sierra Nevada Corp.) As the U.S. administration prepares its new strategy for Afghanistan, the Kabul government and its Western allies are working hard to develop an air force that gives government forces the advantage in their war against Taliban militants. The level of equipment, training and assets falls far short of matching the air assets the Americans still maintain in Afghanistan, but billions of dollars are earmarked for the force which is being built up almost from scratch. “That is what will provide the asymmetric advantage to break the stalemate on the ground,” Brigadier-General Phillip Stewart, commander of TAAC-Air, the Resolute Support mission advising the air force, told Reuters. A four-year, $7 billion expansion plan is aimed at training more flight and maintenance crews and increasing the number of aircraft in the Afghan Air Force (AAF). “In 2014, remember, we (NATO and the U.S. military in Afghanistan) had the best air force in the world and the coalition pulled out and we realized we hadn’t grown the Afghan Air Force,” Stewart said. U.S. officers say the aim is to build a counter-insurgency force able to support troops fighting in remote and forbidding terrain with air strikes, supplies and intelligence. The air force is already conducting some air strikes using Brazilian-designed A-29 Super Tucano light attack aircraft and specially adapted MD-530 scout helicopters and it is building capacity in other areas. Last month, an Afghan air crew parachuted around 400 kg of supplies to an isolated border police outpost, the first time the AAF had conducted an aerial supply drop. “We can do casualty evacuations, we can take cargo, we can take ammunition, we can transport vehicles to different places where they can’t go by road,” said Major Khail Shinwari, an Afghan C-130 Hercules pilot. The AAF has about 120 aircraft in service, ranging from small propeller Cessna 208s to old Soviet-era helicopters, as well as the A-29s, MD-530s and its four veteran C-130 Hercules transporters. In coming years, the old Russian Mi-17s helicopters, which are increasingly difficult to maintain, will be replaced by American UH-60 Black Hawks. The AAF says it is flying up to 140 sorties a day, carrying supplies and providing close air support to troops fighting the Afghan Taliban and Islamic State. But whether it can be built up quickly enough to turn the tide against the stubborn Taliban insurgency is unclear. All the air power of the NATO-led coalition was not enough to defeat the militants and the AAF is nowhere near being able operate alone. U.S. drones, F-16s and Apache attack helicopters are still heavily engaged in areas like Helmand, where U.S. aircraft conducted at least 52 air strikes in the space of five days last week in support of Afghan forces. For the moment, the Afghan A-29s are still using unguided bombs rather than the guided weapons used by the Americans, and the MD-530 helicopters, which came into service in 2015, fire machine guns and rockets attached to their landing gear. “It’s close air support but not as anyone who grew up in the U.S. Air Force would understand it,” Stewart said. “It’s not precision, it’s .50 cal(ibre machine guns) and rockets but they get close to their work and they’re very good.” U.S. trainers say Afghan pilots and crews are being trained to a standard comparable with their American counterparts. But the length of time it takes to train crews - up to four years for pilots and as much as seven years for specialized mechanics - means it will be years before the air force can operate fully independently. For the moment, the emphasis is on building a force suitable for Afghanistan, which means using less complicated equipment such as the C-208s or MD-350 helicopters “at the expense of maybe getting some bigger, sexier platform,” Stewart said. The aim is to increase the effectiveness of the security forces, which advisers hope to get to a point where the Taliban are forced to negotiate a political settlement. As the AAF has grown, however, it has faced increasing pressure from army units to step up operations. Advisers say one of the main risks it faces is overstretch. “They just don’t have the airplanes and sometimes the ground forces will become frustrated because they want more,” Stewart said. 