NEW YORK — Dish Network is offering to buy Sprint Nextel Corp. in a cash-and-stock deal it values at $25.5 billion, saying its bid is superior to that of Japanese phone company SoftBank.

Sprint’s stock jumped almost 15 percent in premarket trading today.

SoftBank Corp. is seeking approval from U.S. authorities for its $20 billion purchase of a 70 percent stake in Sprint Nextel Corp. that would be Japan’s biggest foreign acquisition ever. Sprint previously said that it expected the deal with SoftBank to close during the summer.

The transaction, which was announced in October, was looked at as a way to position Sprint as a stronger competitor against rivals AT&T and Verizon.

Dish, an Englewood, Colo., satellite television company, said today that its proposed transaction includes $17.3 billion in cash and $8.2 billion in stock.

Sprint stockholders would receive $7 per share, which is a 13 percent premium to its Friday closing price of $6.22. This includes $4.76 per share in cash and 0.05953 Dish shares per Sprint share.