Goldman Sachs Group Inc
The Wall Street bank sold 3.03 billion shares, the source said.
The shares represent nearly one-fifth of Goldman's 4.93 percent stake in the Chinese bank, which is the world's biggest lender by market value.
Goldman pledged earlier this year to keep 80 percent of its ICBC stake until April 2010. Under an earlier lockup agreement, Goldman would have been permitted to sell half of its stake in the state-controlled bank this past April and the rest in October.
(Reporting by Steve Eder; Editing by Lisa Von Ahn)