* Swiss Re, SoftBank in preliminary talks - Swiss Re
* Deal could be worth $10 billion or more - WSJ
* SoftBank has investments in Chinese, U.S. insurance firms
* SoftBank's fund arm has invested $27.5 bln in tech firms (Recasts, adds details of SoftBank's investment strategy)
ZURICH/TOKYO, Feb 8 (Reuters) - Swiss Re said it is in preliminary talks to sell a minority stake to SoftBank Group - a deal that reportedly could be worth $10 billion or more, in what would be the Japanese firm's biggest financial services deal to date.
The potential sale of up to one third of the Swiss reinsurer at a premium as reported by the Wall Street Journal would also mark the broadening of already sky-high ambitions that have already seen it raise $93 billion to form its Vision Fund for technology investments.
"Swiss Re informs that it is engaged in preliminary discussions with SoftBank Group Corp regarding a potential minority investment in Swiss Re," the world's second largest reinsurer said.
A SoftBank spokesman declined to comment.
The Japanese company 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 report said, citing people familiar with the matter.
SoftBank could also be aiming to secure another source of cash flow to fund further spending. "Float" - the amount of insurance premiums collected before claims are paid - can be used as cheap funding by insurers, making them attractive to investors.
The news follows SoftBank's announcement on Wednesday that it was preparing to list its domestic telecoms unit, raising further funds that could be used to shore up its finances or make more investments. Local media have estimated the proceeds at $18 billion.
Swiss Re's shares last traded at 90.18 Swiss francs, giving it a market capitalisation of 31.51 billion francs ($34 billion). Its largest shareholder is BlackRock Institutional Trust Co with a 5.02 percent stake, according to Thomson Reuters data.
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 centred on the Vision Fund, the world's largest private equity fund, SoftBank has already funnelled $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.
The purchase of a stake in Swiss Re would be the latest in a constant stream of investments that have made valuing SoftBank difficult and left a "conglomerate discount" weighing on its share price.
SoftBank Group's market capitalisation currently stands at around $90 billion. By contrast, its near 30 percent stake in Alibaba is worth around $130 billion.
It would also come at a time when the reinsurance industry has been hit by rock bottom interest rates that have dampened investment returns with falling industry prices putting pressure on margins.
Swiss Re's nine-month earnings implied a loss of around $1.7 billion from July through September, hit by claims from hurricanes Harvey, Irma and Maria in the United States and from two earthquakes in Mexico. But it said expected a rise in insurance premiums, especially in disaster-hit areas, would help it recover.
SoftBank has made other investments the insurance industry, and has stakes in Chinese online insurer ZhongAn, health insurance claim processing service Ping An HealthKonnect set up by Ping An Insurance Group, and U.S. insurance startup Lemonade.
The Japanese firm's interest-bearing debt at the end of December was 15.8 trillion yen ($144.5 billion), with Son saying on Wednesday he wants to keep debt levels below 3.5 times earnings before interest, taxes, debt and amortization. That ratio stands at 2.8 times currently.
SoftBank shares climbed 1 percent on Thursday, in line with the broader market.
($1 = 0.9443 Swiss francs) ($1 = 109.3500 yen) (Reporting by Brenna Hughes Neghaiwi in Zurich, Sam Nussey in Tokyo; Additional reporting by Pallavi Dewan; Editing by Richard Pullin and Edwina Gibbs)