A top US military commander has announced a review into the American use of air strikes in Afghanistan. Gen David Petraeus, head of US Central Command, said "tactical actions" should not undermine strategic goals. His comments came after Afghan President Hamid Karzai said US air strikes that kill civilians were damaging the fight against terrorism. Washington again expressed regret over recent civilian deaths, but refused to rule out such strikes in the future. On Sunday, hundreds of university students in the Afghan capital, Kabul, protested against air strikes last week targeting Taleban fighters in the western Farah province. Afghan sources said nearly 150 had been killed, but that figure has been disputed by the US. Also on Sunday, the US military denied using white phosphorus in the battle, after local doctors reported treating unusual burns that they said could have been caused by such a chemical. 'Civilians blocked' Afghanistan is a top foreign policy priority for US President Barack Obama's administration, with US forces fighting against an increasingly violent insurgency by Taleban forces. The US is sending 21,000 additional troops to the country, to join an existing force of 38,000. Gen Petraeus, who is responsible for US operations in the region, told Fox News television that he had named a brigadier general "with extensive experience in conventional and special operations" to go to Afghanistan and look at the air strikes issue "more broadly". He said the unnamed military officer would ensure that "our tactical actions don't undermine our strategic goals and objectives". "That's essentially the conversation that President Karzai and I had yesterday on this particular topic," he added. Gen Petraeus also said the Taleban bore "enormous blame" for firing on US troops from the protection of houses, where he said the militants appeared to have forced civilians to remain during the fighting. President Obama's National Security Adviser, Gen James Jones, said the US would "redouble" efforts to limit civilian deaths, but added that it could not hamper its forces in Afghanistan by banning air strikes. "We can't fight with one hand tied behind our back," he told ABC television. 'Fed up' Speaking after talks with the German chancellor in Berlin, Mr Karzai said civilian deaths had to be avoided. "Civilian casualties, of course, is a very serious matter for the Afghan people, (it) also is a serious matter for our allies," he said at a news conference. "It's something that the Afghan people want to be addressed effectively and sooner." Last week, Mr Karzai urged the US to stop the use of such strikes. During the protest in Kabul, students held up banners including one that called America "the biggest terrorist in the world". The protesters also called for those responsible for the air strikes in Farah to be put on trial. "Our people are fed up with Taleban beheadings and suicide bombings. On the other hand, the massacre of civilians by the American forces is a crime that our people will never forget," a statement quoted by AFP news agency said. The US military on Sunday denied that it had used white phosphorus in the battle in Farah, after doctors in the area said they were investigating strange burns on a number of patients. White phosphorus bursts into flames on contact with the air and can cause severe burns. Its use to create light or smoke on open ground is legal, but in built-up areas where civilians are found it is banned under international conventions. The air strike in Farah province overshadowed a summit on Wednesday between the President Barack Obama, Mr Karzai, and his Pakistani counterpart Asif Ali Zardari. Pakistani forces are currently engaged in fierce fighting with Taleban insurgents in the north-west of the country. Source: BBC