Sprint Nextel Corp. yesterday agreed to pay $3.4 billion for Alamosa Holdings Inc., a Texas company that offers Sprint's mobile phone service to 1.5 million subscribers in 19 states.

The deal, which includes assuming $900 million in Alamosa's debt, helped lift shares of Nextel Partners Inc., a Nextel affiliate that is in the process of being bought out by Reston-based Sprint Nextel.

Shares in Kirkland, Wash.-based Nextel Partners, which provides wireless service under the Nextel brand, rose 35 cents, or 1.37 percent, to close at $25.90, reflecting a view that it will command a higher price than Alamosa.

The Alamosa transaction, in which Sprint Nextel agreed to pay $18.75 a share, is the fourth this year in which Sprint Nextel or predecessor Sprint Corp. has agreed to buy out such affiliates. Alamosa and other affiliates helped Sprint expand its coverage by sharing the cost of building out its national wireless network.

Christopher C. King, a senior analyst at Legg Mason Wood Walker Inc., said he estimated that Nextel Partners revenue would rise by 20 to 30 percent next year -- faster than Alamosa's likely increase and worthy of a premium price.

"Given that the growth trajectory at Nextel Partners is greater than that at Alamosa, we would find Sprint Nextel hard-pressed to argue that the valuation of Nextel Partners should be significantly lower than where it is currently trading," King said.

Shareholders in Nextel Partners, which has 1.9 million subscribers in 31 states, voted on Oct. 24 to exercise their right to be bought out by Sprint Nextel. The vote triggered an appraisal process that must be completed by Feb. 11.

Sprint Nextel, formed by the Aug. 12 merger of Sprint Corp. and Nextel Communications Inc., has had talks with its remaining six Sprint affiliates about the possibility of acquiring them or of signing new affiliation agreements.

Sprint Nextel shares rose 23 cents, or 0.92 percent, to close at $25.17, reflecting some relief that it had reached an agreement to buy Alamosa, analysts said. Alamosa shares surged $2.09, or 12.85 percent, to finish at $18.35.