Airbnb transaction would also internationalize the investor base of the online accommodation-sharing group, reflecting the expanding global ambitions of Silicon Valley's leading private companies.
The financing is set to be led by US private equity firm General Atlantic with substantial participation from Beijing-based Hillhouse Capital and investment firm Tiger Global, according to people familiar with the plans. All three are new investors in Airbnb.
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Other new investors in the latest round include UK investment firm Baillie Gifford and US mutual fund group Wellington, with fellow mutual fund companies Fidelity and T Rowe Price topping up their holdings.
News of the impending agreement, which two people familiar with the matter said appeared to be imminent, comes days after it was revealed that Hillhouse was also leading a planned investment in Uber, which has targeted China for a major expansion drive.
The Airbnb financing comes as internet companies command ever higher valuations in both the public and private markets in China and the US, feeding fears of overheating.
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The pre-money figure of $24bn implied by the latest round, before the addition of the extra $1.5bn, compares with a valuation of $10bn in its previous fundraising 15 months ago.