"They've agreed the terms I asked of them two weeks ago so we've reluctantly agreed to sell," said PNE chairman Derek Shaw.
"But it is not a done deal. He still has to have a medical and agree personal terms.
"David told both myself and manager Billy Davies that he wanted to leave and felt Leeds were a big club with lots of potential.
"As soon as he made that clear we had to make sure we got the best deal for Preston.
"Although we intend to keep the figure undisclosed as we intend to go into the market, we have reached the figure we wanted and will now move on and put this business behind us."