Eighteen months after increasing the number of U.S. troops fighting in Afghanistan, President Barack Obama addresses the country Wednesday to make the case for a phased withdrawal of American military forces from the war with the Taliban and al-Qaida.

U.S. media reports say Mr. Obama will announce the withdrawal of about 10,000 troops this year, about 10 percent of the U.S. military contingent in Afghanistan.

White House spokesman Jay Carney says the president will explain how he will implement the strategy he outlined for Afghanistan in December 2009, when he approved a “surge” of 30,000 extra troops and promised the first troops would leave in 18 months. Carney called early reports of the size and speed of the withdrawal “speculation.”

Defense officials have been quoted as saying that Mr. Obama will call for an initial withdrawal of 5,000 troops, followed by an additional 5,000 by the end of 2011.

In his Wednesday night speech at the White House, President Obama is also expected to reaffirm the U.S. and NATO commitment to completely transfer security responsibilities to Afghan forces by 2014. The United States currently has about 100,000 troops in Afghanistan, and media reports estimate the U.S. government is spending $10 billion each month fighting the war.

U.S. Defense Secretary Robert Gates said Tuesday the president has to take into account sustainability at home, both in Congress and among the American public, as well as conditions on the ground in Afghanistan.

Gates acknowledged concerns in the United States about Afghanistan, saying the American people are “tired of a decade of war.” He noted there are “a lot of reservations” in Congress about the war and the level of U.S. commitment.

White House spokesman Carney said the president has remained focused on achieving his objectives in Afghanistan. He noted, however, that Mr. Obama's objectives there do not require defeating the Taliban, but rather “reversing the momentum,” which he says the military has been achieving.