US satellite broadcast carrier DISH Network announced Tuesday that it had made a bid for Clearwire Corp, topping Sprint Nextel's offer for the wireless broadband firm's shares by 11 percent.
DISH said it had submitted a formal offer of $3.30 a share, well above the $2.97 Sprint proposed when it announced its bid in December.
The unsolicited bid, for at least 25 percent and up to all of the shares of Clearwire, cast a question over Sprint's earlier agreement to buy all 50 percent of Clearwire that it did not already own.
Clearwire announced on December 17 that it had accepted Sprint's offer, which is also crucial to another giant deal: Japanese firm Softbank's plan to acquire 70 percent of Sprint.
Softbank shares finished 2.09 percent lower at 3,040 yen ($35) on the Tokyo Stock Exchange Wednesday.
Bellevue, Washington-based Clearwire is sought after for its substantial spectrum holdings and its 4G mobile broadband network, which it is building to handle heavy video transmissions at high speed.
It said in a statement that the DISH offer was "only a preliminary indication of interest" based on acquiring at least 25 percent of Clearwire and also offered to buy spectrum assets for $2.2 billion, and enter into commercial agreements with Clearwire.
Clearwire said that in weighing the DISH bid, it was still bound by its December 17 deal with Sprint.
"Clearwire's ability to enter into strategic transactions is significantly limited by its current contractual arrangements, including the Sprint agreement."
However, it added, its board "has determined that its fiduciary duties require it to engage with DISH to discuss, negotiate and/or provide information in connection with the DISH proposal."
Sprint meanwhile criticized the DISH bid as a series of separate deals and conditions which together as one "makes the proposal not viable."
"Sprint believes its agreement to acquire Clearwire, which offers Clearwire shareholders certain and attractive value, is superior to the highly conditional DISH proposal," it said in a statement.