SoftBank and Saudi Arabia's sovereign wealth fund are preparing to launch a new tech fund that will manage as much as $100 billion, in a move that will create one of the largest tech investment funds in the world.

The new fund, dubbed the SoftBank Vision Fund, will be based in London and seeded with $25 billion from SoftBank and up to $45 billion from Saudi Arabia's sovereign wealth fund over the next five years, according to a statement from Masayoshi Son's Japanese telecoms group.

The unusually large fund underscores investors' enduring appetite for tech sector investments, even amid concerns in Silicon Valley about inflated valuations for late-stage start-ups such as Uber and Airbnb.

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At $100 billion, the new fund would be the same size as all funds raised by U.S. venture capital firms over the last two and a half years, according to data from the National Venture Capital Association.

SoftBank said the fund would be investing over a five-year time horizon, which, at $20 billion a year, would represent roughly a quarter of total annual investments in U.S.-based venture-backed start-ups. It did not say whether it would focus on start-ups or later-stage tech companies.