AT&T Corp. said on Wednesday its board unanimously rejected Comcast Corp.'s unsolicited bid to purchase its AT&T Broadband unit, saying the $40 billion stock offer did not reflect the full value of the No. 1 U.S. cable-television company. 

AT&T said it would explore financial and strategic alternatives for AT&T Broadband, including its previously announced plan to spin off the cable unit. 

AT&T, however, will delay mailing to shareowners the proxy materials regarding the creation of a tracking stock for AT&T Broadband, and planned separation. It had planned to send the proxy materials by the end of the month. 

Comcast, the No. 3 cable television company, launched an unsolicited bid on July 8 to acquire its larger rival, AT&T Broadband, to create the world's largest broadband communications provider with 22 million subscribers. 

One risk arbitrageur, who asked not to be named, said AT&T's statement reflected the company's confidence it could garner a higher price for the business. 

``I think the fact that they authorized the advisers to explore alternatives, they are really confident in the extra value they can get from that division,'' the arbitrageur said. ''Clearly, the restructuring structure they already have in place there allows them to leverage into a higher bid.'' 

After the Comcast bid emerged, Cablevision Systems Corp. and Cox Communications Inc. also expressed interest in buying AT&T Broadband, according to recent media reports. 

In addition to the price, AT&T also said it had concerns about the proposed voting structure. Under Comcast's proposal, AT&T shareholders would have a majority equity interest in the combined company, but less voting control. 

The Roberts family, which began Comcast in 1963, owns about 2 percent of the company but holds 86 percent voting control. In a deal with AT&T Broadband, the Roberts' voting control would drop to below 50 percent, but the family would still have a disproportionate amount of control given its equity stake. 

AT&T is in the midst of a massive restructuring to split its major businesses -- broadband, business, consumer and wireless -- into three separate companies with four stocks. The wireless telephone services business, AT&T Wireless, was separated on July 9. 

AT&T emphasized that it remained committed to separating its consumer and business operations from AT&T Broadband, and creating a separate tracking stock designed to represent the financial performance of AT&T Consumer.