NEW YOR — Bellevue-based Clearwire, which operates a wireless data network, on Monday said a second shareholder advisory firm, Egan-Jones, has endorsed the buyout of minority shareholders by Sprint Nextel.

Egan-Jones joins ISS in supporting the $2.2 billion deal, but it faces opposition from shareholders and a third shareholder advisory firm, Glass Lewis.

Analyst Kevin Smithen with Macquarie Securities said in a research note Monday that the shareholder vote on the deal, scheduled for next Tuesday, could fail unless Sprint sweetens the bid.

Clearwire shares fell 8 cents, or 2.e percent, to $3.18 in midday trading in New York. That’s above Sprint’s offer of $2.97 per share for the 49 percent of the company it doesn’t already own.

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Clearwire’s executive chairman John Stanton sent a letter to shareholders on Monday, urging support for the deal. It repeated arguments from a previous letter: Clearwire faces a difficult future on its own, it hasn’t been able to find other buyers, and Sprint’s offer is more than double the price of Clearwire shares before October, when speculation mounted that Sprint could buy out minority shareholders.

Sprint is Clearwire’s only major wholesale customer, and uses its network to provide “Sprint 4G” service.

Crest Financial, the largest minority shareholder, said the sales process has been “unfair” and “coercive,” and Clearwire’s board is settling for a “grossly inadequate price.”