Clearwire Corp shareholder Mount Kellett Capital Management LP said on Friday that Sprint Nextel Corp's $2.90 per share bid for Clearwire is "grossly undervalued."

"There is no rush for the company to sell itself at a deeply discounted price," the shareholder said in an open letter to Clearwire. Mount Kellett owns 53.2 million shares or about 3.6 percent of Clearwire's stock.

Other shareholders have also complained about the value of the offer from Sprint, which already owns 50.45 percent of Clearwire. Sprint said on Thursday that it offered to buy the rest of the company for $2.1 billion or $2.90 per share.

(Reporting By Sinead Carew; Editing by Gerald E. McCormick)