MOSCOW, October 13 (RIA Novosti) - The U.S. could send an additional 13,000 troops to Afghanistan, the Washington Post said on Tuesday, citing defense ministry sources.

U.S. President Barack Obama earlier pledged to increase the number U.S. military personnel in the war-ravaged country by 21,000. According to the paper, the troops will be boosted by a supply contingent of 13,000.

"Obama authorized the whole thing. The only thing you saw announced in a press release was the 21,000," the paper quoted a "defense official familiar with the troop-approval process' as saying. The U.S. already has a 68,000-strong military contingent in the war-ravaged country.

The additional troops would include mainly "engineers, medical personnel, intelligence experts and military police," the paper said.

The White House and the Pentagon have given slightly different comments on the issue. A White House spokesman Tommy Vietor said Obama did not approve any increase in troops after his March 27 speech to the Congress.

A spokesman for the Pentagon, Bryan Whitman, however, confirmed the report without giving the exact amounts involved in the supply contingent.

"The 21,000 are only combat forces, and when the combat forces go in, there are a certain amount of additional forces that are required," he said.