Japanese mobile carrier SoftBank Corp. increased its offer to $21.6 billion or 7.5 percent in order to counter a bid set by Dish Network Corp.'s Charlie Egen for acquisition of Sprint Nextel Corp.

A new $5 billion boost into the target for a 78 percent stake together with a payment of $16.6 billion is set to be made by Softbank to Sprint stockholders, said the Japanese company. Sprint said however, that the deal is not final and the the company is giving DISH until June 18 to make its "best and final" offer. Sprit added that DISH's current offer which stands at $25.5 billion is not at all "actionable."

Masayoshi Son, controller of SoftBank Corp.,is believed to have the backing of Sprint's decision makers.

"If SoftBank can't buy Sprint, it will mess up Son's strategy for growth, so this is very positive," said Masamitsu Ohki, a fund manager at Tokyo hedge fund Stats Investment Management Co. "This would be the first step for his global strategy," said Ohki.

Son cannot grow from pursuing the Japanese market alone, added Ohkii.