US Defence Secretary Robert Gates says meeting President Barack Obama's 22 January deadline for closing the Guantanamo Bay camp will be "tough".
In interviews with US TV networks, Mr Gates said that closing the camp was proving more complicated than expected.
Mr Gates played down the importance of possibly pushing the date back.
More than 220 inmates are in the camp. Some are expected to be sent to other countries, others could face military tribunals or be tried in US courts.
In the latest case of former detainees being sent abroad, two men thought to be citizens of Uzbekistan landed in Ireland on Saturday to be resettled there. read more
