(CNN) -- An influential adviser to the U.S. commander in Afghanistan declared Friday that anything less than 25,000 extra international troops in the country would not be enough to win.
David Kilcullen, who also advised U.S. commanders in Iraq, told CNN's Christiane Amanpour the window of opportunity to turn around the war is closing.
Kilcullen's comments came as President Barack Obama, only hours after being awarded the Nobel Peace Prize, again met with his top advisers to discuss strategy and troop levels in Afghanistan.
The U.S. commander in Afghanistan, Gen. Stanley McChrystal, is reportedly asking for up to 40,000 extra troops. Some reports say there is an option on the table to send 60,000 additional troops, almost doubling the U.S. force now in the country.