Swiss Re said on Wednesday that talks with SoftBank over a minority stake of no more than 10 percent in the reinsurance giant were continuing and "at an early stage".
Swiss Re also reiterated that it was not considering the issuance of new capital for the possible investment by the Japanese company.
The reinsurer said that the minority investment was "currently expected not to exceed 10 percent" and that the two companies were also exploring strategic cooperation.
Swiss Re, which is briefing investors on Wednesday, emphasized that talks were preliminary.
"There is no certainty that any minority investment or strategic partnership will be agreed, or as to any terms, timing, or form of any such investment or partnership," it said.
The potential deal of a stake by SoftBank would underscore SoftBank's ambitions to broaden its investments, which already include its $93 billion Vision Fund for technology projects.
Analysts have said SoftBank could be attracted by Swiss Re's research capabilities, undervalued stock, and cash generation.
SoftBank plans to offer Swiss Re's insurance products directly to users of other companies it has invested in, such as Uber and WeWork, the Wall Street Journal has reported, citing people familiar with the matter.
SoftBank founder Masayoshi Son has said he wants to build a group of industry-leading companies that, powered by technological advancements in artificial intelligence and interconnected devices, will endure for 300 years.
Through its investment arm centered on the Vision Fund, the world's largest private equity fund, SoftBank has already funneled $27.5 billion into tech firms around the world. That could bring a huge number of potential insurance customers - from ride-share drivers to dog walking app users - into what Son calls his "synergy group" of companies.