Significantly, however, delays by Secretary of Defense Chuck Hagel in signing off on the arrangement placed it in jeopardy. Mr. Hagel’s slow pace this year in approving proposed transfers of low-level detainees contributed to larger tensions with the White House before his resignation under pressure last month.

Will Guantánamo close on Carter's watch?

Ashton Carter, if confirmed as Defense secretary, would play a central role in President Obama's promise to close the Guantánamo Bay detention facility before he leaves office.

Minutes after Obama announced Carter's nomination Friday, a top human rights organization urged Carter to help the president cross "the finish line."
“From day one Carter will face a full agenda, and will play a pivotal role in overseeing policies with human rights at their core,” said Human Rights First’s Raha Wala.

As head of the Pentagon, Carter would be responsible for personally approving any releases from the facility and certifying that the detainee would not return to the battlefield.