US Defense Secretary Robert Gates said Thursday it was possible that 2011 could see a decisive turning point in the war in Afghanistan against Taliban insurgents.

"My own view is that this year is a critical year. We have driven the Taliban out of areas they have controlled for years, including their heartland," Gates told reporters at the Pentagon.

"If we can prevent them this year from retaking the areas that we have taken away from them, and we can continue to expand the security bubble, I think it's possible that by the end of this year we'll have turned the corner, just because of the Taliban being driven out and more importantly, kept out."

The United States has about 100,000 troops in Afghanistan, supported by 48,000 troops from coalition allies.

NATO commanders expect an increase in violence in the spring. For now, many insurgents are occupied by the poppy harvest, which should continue until mid-May, according to General James Cartwright, vice chairman of the Joint Chiefs of Staff.

"So the character of the fighting right now is probably more along the lines of the individual spectacular attack, rather than groups of people," Cartwright said.