Clearwire's (NASDAQ: CLWR) largest minority stockholder, Crest Financial, is still urging other shareholders to vote against Sprint Nextel's (S) proposed buyout of their company, even after Sprint raised its bid, according to Crest's filing with the SEC late yesterday.

Earlier this week, just prior to a special shareholders' meeting called to vote on Sprint's original $2.97-a-share offer, Sprint upped its offer to $3.40 a share. Clearwire's board has approved the new offer.

Crest wants to wait until the battle between DISH Network (DISH) and Japanese telecom SoftBank for Sprint "is resolved because both DISH and SoftBank suggested in public statements that ownership of Clearwire is among the primary reasons for their desire to acquire control of Sprint."

Crest wrote that "A rejection of the Proposed Sprint-Clearwire Merger ... would enable [Clearwire] to conduct a direct competitive bidding process for Clearwire." Clearwire's own financial advisors "suggested that the implied equity value of Clearwire could be significantly higher than the $3.40 offered by Sprint," according to Crest.

The Clearwire shareholders' vote on Sprint's new offer has been rescheduled for May 31.The Sprint shareholders' vote on whether to accept SoftBank's bid for 70% of their company is not scheduled until June 12.