Private equity firm TPG Capital
It is the latest private equity fund to turn either to the Middle East or Asia for capital, and the deal will likely raise questions about whether TPG eventually wants to follow a handful of its rivals in going public.
However, a source close to TPG previously told Reuters that the firm has no plans to go public.
TPG told its investors in a recent letter that it had agreed to sell a small stake, said the source who spoke to Reuters and has seen the letter. The letter did not specify who the buyers were.
The letter said that the capital would be used to fund the expansion of TPG's existing business lines and firm-wide operations, said the source.
TPG declined comment. A spokeswoman for the Singapore investment group was not immediately available to comment, nor was anyone from the Kuwait fund available for comment.
The Wall Street Journal, which earlier reported the news, said the deal values TPG at $11 billion.
TPG, founded in 1992 and run by private equity pioneer David Bonderman, has more than $47 billion of capital under management. It has offices around the world, including in Singapore, according to its website.
Rivals Blackstone and Carlyle have had sovereign wealth fund investors for several years.
Abu Dhabi bought a $1.35 billion stake in Carlyle Group in September 2007, and sovereign wealth fund China Investment Corp owns 10 percent of Blackstone.
CIC's investment in Blackstone has suffered. It bought in just before Blackstone went public in 2007 at $31 a share. Blackstone's shares are currently trading at $18.01 -- although they have rallied from a low of below $4.
TPG and the Government of Singapore Investment Corp (GIC) have invested together in deals in the past. In December, TPG and GIC bought a stake in Indonesia coal contractor PT Delta Dunia Makmur for $331 million.
GIC, which is estimated to have a portfolio of more than $200 billion, said in February the United States will continue to be a prime destination for years to come.
Tony Tan, GIC's deputy chairman, said recently that despite global economic rebalancing and rapid growth in China and other emerging economies, the United States would remain the single most important source of global prosperity.
GIC's key investments include a substantial stake in Citigroup
According to GIC's last annual report, issued in September, the United States accounts for 36 percent of its investments, the highest of any country.
(Additional reporting by Saeed Azhar in Singapore; Editing by Gerald E. McCormick and Steve Orlofsky)