President Barack Obama has reaffirmed his plans to start withdrawing U.S troops from Afghanistan in 2011.

Speaking in an interview with Australian television broadcast Thursday, Obama said of Afghanistan that United States and its allies "can't be there in perpetuity."

Obama told the Australian Broadcasting Corp. that he did not agree that the situation in Afghanistan was getting worse, saying the Taliban's momentum had been "blunted" since he came to office.

But winning the nearly nine-year-old war remained a difficult task, he said.

The interview comes ahead of a planned trip by Obama to Australia and Indonesia in June.