NEW YORK (Bloomberg) — American International Group, the world's biggest insurer, raised $3.5 billion to invest in infrastructure buyouts.

Two-thirds of the money has been committed for investments, AIG Highstar Capital said in a statement. More than 90 percent came from outside investors, AIG said.

The private equity unit has stakes in companies that run power plants, waste treatment facilities and shipping terminals, including Ports America, acquired from Dubai-owned DP World in March.

AIG collects fees to manage private equity and hedge fund investments for clients and also has put $25.5 billion of its own money into the holdings to back insurance policies.

Income from the partnerships totaling $2.2 billion through the end of June helped the New York-based company beat analysts' profit forecasts this year. The assets made up 3 percent of the company's $828.8 billion holdings as of June 30.