US President Barack Obama has outlined a new Afghanistan policy that will send an additional 30,000 US troops to Afghanistan, and start their withdrawal in July 2011.

The "surge" of 30,000 troops is expected to be completed by the summer of 2010.

"The 30,000 additional troops that I am announcing tonight will deploy in the first part of 2010 the fastest pace possible so that they can target the insurgency and secure key population centres," Obama said.

"They will increase our ability to train competent Afghan Security Forces, and to partner with them so that more Afghans can get into the fight. And they will help create the conditions for the United States to transfer responsibility to the Afghans," the President said.