The U.S. Was Resettling Guantánamo Prisoners. The Hamas Attack Halted Those Plans.

The Biden administration was poised to send about a dozen detainees at Guantánamo Bay to Oman for resettlement last year, but it abruptly halted the secret operation amid questions from Congress about security in the Middle East after Hamas attacked Israel, according to administration officials.

None of the prisoners have ever been charged with crimes, and all of them had been cleared for transfer by national security review panels.

A military cargo plane was already on the runway at Guantánamo Bay ready to airlift the group of Yemeni prisoners to Oman when the trip was called off, people familiar with the military operation said.

Belongings they could take with them had been collected, signaling to the prisoners that they would soon be going. Then the plane flew away empty, and their belongings were returned.

Details of such operations are classified for the security of the U.S. military aircrews that transport the men. But U.S. officials, speaking on the condition of anonymity because detainee movements are considered secret until completed, acknowledged the aborted mission after NBC published an account of it on Monday.

The delayed transfer illustrates the Biden administration’s continuing struggle to find countries willing to resettle and keep watch on the 16 cleared detainees, who are among the 30 men held at Guantánamo. Such deals require diplomacy, participation by the intelligence community and advance notice to Congress.