WASHINGTON (Reuters) - The Pentagon said on Monday that the security situation in Afghanistan was "not going in the right direction" as Taliban militants captured a sixth provincial Afghan capital.

       Pentagon spokesman John Kirby said the United States was deeply concerned about the trend, but that Afghan security forces had the capability to fight the insurgent group.

       "These are their military forces, these are their provincial capitals, their people to defend and it's really going to come down to the leadership that they're willing to exude here at this particular moment," Kirby said.

       (Reporting by Idrees Ali; editing by Jonathan Oatis)