SoftBank Group Corp. is considering seeking a valuation of about $90 billion for its domestic wireless business in a planned initial public offering, according to sources.

SoftBank is speaking to advisers about selling a third — or about $30 billion — of the business in the IPO, the sources said, asking not to be identified as the talks aren't public.

Discussions are preliminary and the final valuation will depend on investors' feedback, they said. SoftBank rose 6.5 percent in Tokyo on Tuesday, the biggest increase since June, following strong first-quarter results.