Delays continue to beset a proposed bilateral security agreement between the U.S. and Afghanistan. The pact would govern U.S. troops if they remain in Afghanistan past 2014. Deadlines have come and gone, but still no agreement has been signed by the two parties. Now, the situation seems to have deepened into a political standoff between the Pentagon and Afghan President Hamid Karzai. To understand how it got to this point, Robert Siegel turns to Sean Carberry, reporting from Kabul, and Tom Bowman, NPR's Pentagon correspondent.