DISH Network will "admit we failed" and sell its cache of wireless spectrum worth billions of dollars if the satellite TV provider fails to land a partner to help it realize ambitious plans to build a wireless network, Chairman Charlie Ergen conceded Monday at an industry event. Ergen insisted that its bid to pre-empt Sprint Nextel's offer for wireless service provider Clearwire is real. "We're serious about it. Our offer is good for shareholders. Sprint will have to do more to keep us out," he said. Ergen also said DISH bought the Blockbuster video chain in order to sell wireless service, a move that was blocked by regulatory delays.