America's top military officer says the U.S. threat to withdraw all troops out of Afghanistan if no security pact is signed may encourage the enemy and lead some Afghan forces to align with the Taliban.

Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, says the announcement of President Barack Obama's order to begin planning for a total withdrawal also makes Afghan military leaders anxious and eats away at their troops' confidence.

Speaking at the end of a long day of meetings with his commanders in Afghanistan, Dempsey said Wednesday he wanted to make sure they knew there is still a lot of work to do this year, and that they can't let worries about next year distract them.