The move follows a registration statement by GM last month making it easier for the Treasury to sell its remaining 241.7 million shares, or nearly 18 percent, of common stock of the No. 1 U.S. automaker.
It also will bring the Detroit company a step closer to eliminating the stigma of government ownership.
Executives have chafed under the "Government Motors" tag since the government-sponsored bailout and bankruptcy in 2009 that left the Treasury with a 60.8 percent share of GM.
After reporting better-than-expected first-quarter earnings last week, GM came within 56 cents of its November 2010 IPO price of $33.
"We are pleased with the progress to date and will continue exiting this investment in accordance with our previously announced plan and timetable, and in a manner that maximizes returns for taxpayers," Tim Massad, Treasury assistant secretary for financial stability, said in a statement.
In December, the department said it would fully exit its GM investments within the following 12 to 15 months, "subject to market conditions." But it gave no specific dates for the resumption of share offerings.
Executives have said that putting this behind them will improve GM's image and boost sales.
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The automaker's shares were not much moved by the news. Just after midday, GM shares were down 5 cents at $32.05 on the New York Stock Exchange.