SoftBank Corp has asked investment banks not to finance a rival bid for Sprint Nextel Corp by Dish Network Corp, saying doing so could hurt their chances of gaining a coveted role in the highly anticipated public offering of Alibaba Group Holding Ltd, according to two people with knowledge of the matter.

Japanese telecom giant SoftBank, which is a big shareholder in Chinese e-commerce giant Alibaba with a 33 percent stake, is locked in an escalating bidding war with Dish, after the U.S. satellite TV provider made a $25.5 billion proposal for Sprint in April.

SoftBank, which has an existing agreement with Sprint to buy 70 percent of the U.S. wireless carrier for $20.1 billion, has heavily criticized Dish's offer, saying the rival bid does not have committed financing in place.

Dish, which has said it would need to raise $9 billion in debt to finance the offer, is currently in the process of lining up financing, but having challenges partly because banks have come under from pressure from SoftBank not to join the Dish financing, the people said on Friday.

At least one major Wall Street bank already withdrew from financing the Dish bid because of the bank's relationship with SoftBank and its likely role in the Alibaba IPO, they added.

Alibaba declined to comment, but a person close to the company said while SoftBank is a major investor, it does not make decisions for Alibaba management. Alibaba has no timetable for an IPO yet and has not hired underwriters.

Sprint, SoftBank and Dish declined to comment.

(Reporting by Soyoung Kim and Olivia Oran in New York; Editing by Gary Hill)