WASHINGTON (AP) — In another challenge to President Barack Obama's efforts to close the Guantanamo Bay prison, administration officials say a ban on transferring detainees to Yemen has been effectively pushed back into place.

That's because of security concerns in the volatile Middle Eastern nation.

While Obama approved sending detainees back to Yemen nearly two years ago, his administration has yet to use that authority. And officials say concerns about the threat posed by a Yemeni-based al-Qaida offshoot have removed that option for the foreseeable future. The officials say that could change if conditions improve.

Meanwhile, the administration is working on agreements with third countries willing to take Yemenis who are cleared to leave the prison.

The officials describe the stance on condition of anonymity without authority to speak on the record.