WASHINGTON — An unreleased Pentagon report provides new details concluding that about one in seven of the 534 prisoners already transferred abroad from the detention center in Guantanamo Bay, Cuba, has returned to terrorism or militant activity, according to administration officials.

The conclusion could strengthen the arguments of critics who have warned against releasing any more prisoners as part of President Barack Obama’s plan to close the prison by January. Past Pentagon reports on Guantanamo recidivism have been met with skepticism from civil liberties groups and criticized for their lack of detail.

The Pentagon promised in January that the latest report would be released soon, but spokesman Bryan Whitman said this week that the findings were still “under review.”

Two administration officials who spoke on condition of anonymity said the report was being held up by Defense Department employees fearful of upsetting the White House, at a time when even congressional Democrats have begun to show misgivings over Obama’s plan to close Guantanamo.

The White House has said that Obama will provide further details about those plans in a speech this morning at the National Archives.