The US is aiming to send 20 to 30,000 extra troops to Afghanistan by the beginning of next summer.Washington is already sending some 3,000 extra troops in January and another 2,800 by spring. Previously officials have said the number would be made up to 20,000 in the next 12 to 18 months once approved by the US administration. US army commanders say the troops are needed to combat a growing Taliban insurgency. Chairman of the US Joint Chiefs of Staff Admiral Mike Mullen told reporters in Kabul: “Available forces are directly tied to forces in Iraq. As we look to the possibility of reducing forces in Iraq over the course of the next year, the availability of forces to come here in Afghanistan will increase.” Meanwhile three Danish soldiers serving with NATO forces in Helmand province were killed and another was injured when their armoured vehicle drove over a roadside bomb. The deaths, near the town of Gereshk, bring to 21 the number of Danish troops killed in the country since Copenhagen deployed soldiers there as part of the International Security Assistance Force in 2001.