Clearwire Corporation (NASDAQ:CLWR) shareholders are certainly not thrilled with the $2.1 billion offer from Sprint Nextel Corporation (NYSE:S). Reuters reports today that Mount Kellett Capital Management LP, which owns less than 4 percent of Clearwire’s stock, issued a letter urging the company’s board not to take the deal.

ValueWalk has been following the potential deal between Clearwire Corporation (NASDAQ:CLWR) and Sprint Nextel Corporation (NYSE:S) since it surfaced. Shares of Clearwire have increased dramatically since the deal was announced just days ago, rising from around $2.40 per share to about $3.20 per share, where the stock is trading mostly flat today.

According to Reuters, Mount Kellett feels that Sprint’s offer of $2.90 per share greatly undervalues Clearwire’s worth. It also warned about Sprint Nextel Corporation (NYSE:S)’s $800 million in interim financing for the cash-strapped company, saying that the extra cash would dilute the value of current shareholders’ holdings in the company.

Softbank Corp (TYO:9984), which is in the process of purchasing 70 percent of Sprint, placed a cap on the company’s offer to purchase Clearwire Corporation (NASDAQ:CLWR) at $2.97 per share, but Reuters reports that shareholders feel that the company is worth close to $5 per share.

Clearwire has been struggling recently because it needs capital to update its network. The company said it has enough cash to last until the third quarter. Sprint owns more than 50 percent of Clearwire, and if it can acquire Clearwire, it would be able to compete more with AT&T Inc. (NYSE:T) and Verizon Communications Inc. (NYSE:VZ).

According to Reuters, an anonymous source also said Clearwire may be considering alternatives other than Sprint’s deal.