The U.S. Treasury does not plan to start selling its remaining shares in General Motors Co until August at the earliest, after the automaker's second-quarter financial results, people familiar with the matter said.

The Treasury, which holds a 32 percent stake in the top U.S. automaker, plans to wait on a secondary offering in light of GM's recent share performance, and the earliest possible time for its follow-on sale is August, these people said.

The sources asked not to be identified because the matter is not public.

The U.S. government is also opposed to the idea of selling a portion of its shares directly to GM, although such a transaction was suggested as a possible option, these people said. A Treasury spokesman declined to comment.

Six months after GM's $23.1 billion initial public offering, investors have been speculating that the U.S. Treasury is itching to sell a big part of its remaining stake after the lock-up period for selling by major shareholders expires on May 22.

The administration of U.S. President Barack Obama received a nearly 61 percent stake in GM two years ago in return for its $50 billion bailout of the automaker.

Before the IPO, GM was touted as a restructured company with a drastically lower break-even point in North America, a leading market position in China and other emerging markets, turnaround potential in Europe and a strong lineup of new fuel-efficient cars such as the Chevrolet Cruze and plug-in hybrid electric Chevy Volt.

But oil prices spiked, hurting sales of higher-margin trucks, and generous discounts to new-car buyers continued.

Worries about supply disruptions following the earthquake in Japan have also unsettled investors anxious for the Treasury to exit its position in GM.

GM shares were up 3 cents in early afternoon trading on the New York Stock Exchange at $31.33.

(Reporting by Soyoung Kim; Editing by Derek Caney and Robert MacMillan)