The Treasury, which holds a 32 percent stake in the top U.S. automaker, will 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 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 to help alleviate the overhang for GM's stock stemming from roughly $16 billion worth of shares held by Treasury, these people said.

The Treasury has also decided to delay a secondary offering for at least several months partly because it wanted to avoid the process of another S-1 regulatory filing — which would require a potentially lengthy review by the U.S. Securities and Exchange Commission — the sources said.

Beginning July 1, GM is eligible to file for an S-3 filing instead, which would allow Treasury to sell shares without having to address a review from the SEC.

The sources asked not to be identified because the matter is not public. A Treasury spokesman declined to comment.

"The timing of any offering is entirely in the hands of the Treasury department. Our focus continues to be on profitable global growth, further strengthening our balance sheet and fully funding our pension plan," GM spokesman Jim Cain said.

While the Treasury is looking at the months of August, September, November and December for a possible secondary offering, it has not committed to any specific time frame, the people familiar with the matter said.

LIMITED WINDOW

August has a very limited window since Treasury would need to see GM's quarterly financial results before any follow-on sale and Wall Street is shut down for much of the month, these people said.

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 13 cents at $31.43 Thursday afternoon, below the IPO price of $33.

The New York Times reported earlier Thursday that Treasury Department officials are planning a secondary sale of GM shares for late summer or early fall, later than many investors expected.