US Defense Secretary Robert Gates has blocked the public release of any more pictures of foreign detainees abused by their US captors, saying their release would endanger American soldiers. The Obama administration filed a brief with the Supreme Court late Friday saying that Gates has invoked new powers blocking the release of the photos. The American Civil Liberties Union had sued for the release of 21 color photographs showing prisoners in Afghanistan and Iraq being abused by Americans. Federal courts had rejected the government's arguments to block their release, so Congress gave Gates new powers to keep them private under a law signed by President Barack Obama last month. Gates' order specifically cites the 21 pictures sought by the ACLU, plus 23 additional ones cited in a ruling by the U.S. Court of Appeals for the 2nd Circuit.