President Obama has ordered the Pentagon to begin drafting plans for a complete withdrawal of American troops from Afghanistan by the year's end in case the Bilateral Security Agreement is not signed, the White House announced Tuesday.

Obama notified his counterpart, Afghan President Hamid Karzai, of the decision in a phone call.

“President Obama told President Karzai that because he has demonstrated that it is unlikely that he will sign the BSA, the United States is moving forward with additional contingency planning,” said the White House 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,” the statement added.

Afghan and U.S. negotiators last year agreed on a postwar security pact governing the role of American forces after the 2014 drawdown of the NATO-led mission.

But Karzai, despite the deal being approved by a council of Afghan elders, has refused to sign, saying that the next president of his country should approve the agreement.

Afghan elections are slated for April, but the administration has repeatedly pressed Karzai to quickly sign the deal, arguing that they cannot delay planning for the eventual withdrawal of U.S. forces.

Critics say that without an agreement and U.S. troop presence, the international community risks seeing their decade-plus effort to build a stable Afghanistan lost.

Defense Secretary Chuck Hagel on Tuesday said he would “move ahead” with the president’s order, calling it a “prudent step.”

"At President Obama's direction, and with my strong support, the Department of Defense will move ahead with additional contingency planning to ensure adequate plans are 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,” said Hagel in a statement.

“Our force posture over the next several months will provide various options for political leaders in the United States and NATO,” he added. “And during this time DoD will still continue planning for U.S. participation in a NATO-led mission focused on training, advising, and assisting Afghan security forces, as well as a narrowly focused counterterrorism mission.”

The White House, though, added that the U.S. “will leave open the possibility” that a security deal with Kabul could be finalized this year.

“However, the longer we go without a BSA, the more challenging it will be to plan and execute any U.S. mission. Furthermore, the longer we go without a BSA, the more likely it will be that any post-2014 U.S. mission will be smaller in scale and ambition,” the statement warned.

The White House said Obama and Karzai also discussed “preparations for Afghanistan’s coming elections, [and] Afghan-led peace and reconciliation efforts.”

Obama “affirmed the United States’ support for a fair, credible, timely, and Afghan-led process.”

“As Afghans soon take the important step of heading to the election polls, they should know that the United States will be committed to supporting the Afghan security forces as they make preparations to secure the Afghan elections,” the statement said.

The president also assured his Afghan counterpart that the U.S. would not back any candidate in the contest.