Preston have rejected a fourth bid for Healy, a package totaling £600k and the Leeds board have stated that they are not prepared to up their offer past what they believe is "a very attractive deal" for the Northern Ireland international
Blackwell said on Leeds' official website: "I know we are not a million miles away. We are very close to doing something, however, until it's done it isn't done and that's the frustration.
"The tenacity amongst the team and the will to work hard for each other whilst grinding out results without the likes of David Healy means we will carry on doing just that until the situation can be resolved one way or another.
"At the point when it completely breaks down I will look at other targets, which I have got to start to do anyway because the whole thing is dragging on.
"Preston want to keep their best player and I do not blame them for that."