Bryan Singer's newest accuser -- the man who says Singer sexually assaulted him as a teenager following the "Superman Returns" premiere party in London in 2006 -- is expected to reveal himself at a news conference at any moment ... we're streaming LIVE.
TMZ broke the story ... the anonymous accuser claims Singer assaulted him when he was just 17, molesting him ... then asking the boy to sit on his chest and ejaculate on top of him. Singer has adamantly denied the allegations.
