President Barack Obama has warned his Afghan counterpart Hamid Karzai that the U.S. may pull all of its troops out of his country by the year's end.
Obama conveyed the message in a phone call to Karzai, who has refused to sign a security agreement.
The U.S. insists this agreement must be in place before it commits to leaving some troops behind for counter-insurgent operations and training. The U.S. has had troops in Afghanistan since 2001 when it toppled the Taliban.
Correspondents say the disagreement over the bilateral security agreement is the latest step in the long and deteriorating relationship between Washington and Karzai, who was once seen as a key U.S. ally.
"President Obama told President Karzai that because he has demonstrated that it is unlikely that he will sign the BSA (Bilateral Security Agreement), the United States is moving forward with additional contingency planning," the White House said in a statement.
"Specifically, President Obama has asked the Pentagon to ensure that it has adequate plans in place to accomplish an orderly withdrawal by the end of the year should the United States not keep any troops in Afghanistan after 2014."
Read the full story at BBC News.