According to the New York Times, Senator Hillary Clinton will suspend her campaign on Friday and officially endorse Barack Obama on Friday June 6th. The move was suggested to her by her strongest supporters in Washington after being pressured by her own campaign strategists which suggests that Clinton was not prepared to concede until this afternoon.
More from the New York Times:
http://www.nytimes.com/2008/06/05/us/politics/04cnd-campaign.html?ref=us