The US is to send an additional 1,400 marines to southern Afghanistan in an effort to counter a Taliban offensive, a Pentagon official has said.
The marines are now being notified of the deployment and are scheduled to leave within several weeks, the defence department said.
The US hopes to "apply pressure on the enemy during the winter", a department spokesman said.
The US plans to begin withdrawing troops from the country in July.
Defence secretary Robert Gates had "approved additional marine forces to southern Afghanistan to exploit and consolidate gains already achieved and apply pressure on the enemy during the winter campaign", Defence Department spokesman Col Dave Lapan said.
President Barack Obama approved a troop surge of 30,000 troops roughly one year ago. But the president gave Mr Gates leeway to add an extra 3,000 forces, if necessary.
Following the publication of the US annual strategy review last month, Mr Obama said the US was "on track" to achieve its goals in Afghanistan.
The review stated that the US had made enough progress to start a "responsible reduction" of forces in July 2011. BBC News
