Bloomberg Businessweek article.
Simply put, BP plays too big a role in the US market to let it go under. If it does, the loss will compromise what little energy security we possess.
So Obama backing off some, saying on 16 June that "BP is a strong and viable company, and it is in all of our interests that it remain so."
BP's skill in negotiating its way into strategically important regions--like post-Saddam Iraq--is considered a serious US national security asset.