KABUL, Afghanistan -- U.S. Defense Secretary Chuck Hagel paid a surprise visit to American forces in Afghanistan amid a stubborn stand-off between the U.S. and Afghan leaders over a security agreement that President Hamid Karzai refuses to sign despite increasing pressure.
Hagel, whose unannounced visit was reportedly planned weeks ago, is a central player in the dispute, but he said he had no plans to meet with Karzai during his stopover.
"My purpose for being here is to spend the day with troops and thank them for the tough work they do," Hagel said. He added that his intention was to spend time with troops during the holiday season.
The U.S. has made its position on the security agreement clear and Karzai has tentatively endorsed the deal. Still, he refuses to sign it after it was approved by a council of tribal elders known as the Loya Jirga. The council said the agreement with the U.S. should be signed by the end of December, as U.S. officials have demanded.
Hagel said he was "surprised" when Karzai indicated that he wasn't ready to sign the agreement.
Karzai says he wants his successor to decide after the April 5 elections. Washington and NATO officials say they want a quick decision on the bilateral security agreement, which allows U.S. troops to stay in Afghanistan after 2014 to do training and some counterterrorism missions.
Without a signed agreement, all U.S. troops would leave at the end of next year, along with all foreign forces. Military leaders have said they need time to plan and coordinate with allies for the post-2014 mission, which could involve around 8,000 U.S. forces and another 6,000 allies troops.
Karzai has said he won't sign any agreement that allows continued raids on Afghan homes. Under Afghan law, any agreement must be signed twice — once to get it to parliament and, if approved, then by Karzai alone in his capacity as president.
Pentagon spokesman Carl Woog said Hagel is traveling to Afghanistan "to thank troops for their service fighting far away from home and commend the progress they have made this year" in improving the Afghan security forces. He said Hagel planned to meet with Afghan Minister of Defense Bismillah Khan Mohammadi and Minister of Interior Mohammad Umer Daudzai. He also planned to travel around the country to visit with coalition service members.
Earlier this week, Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, told reporters in Washington that the White House has not instructed him to plan for a so-called "zero option" that would leave no U.S. troops in Afghanistan after 2014. But he cautioned that it is a possibility, given the ongoing impasse.
This is Hagel's second trip to Afghanistan since he began as defense chief early this year.
His visit in March was marked by drama. His less than three day stay was riddled with bombings, security threats, political gridlock and wild accusations from Karzai.
A suicide bomber targeted the Afghan defense ministry a day before Hagel was scheduled to go there, and the Pentagon chief had to cancel a planned news conference because of a security threat.
In addition, Karzai accused the U.S. of colluding with the Taliban. The comments drew sharp rebukes from other U.S. officials as days passed.
NBC's Simon Moya-Smith contributed to this report.