The government pledged to sell its remaining 300 million shares on the open market and shed its entire ownership stake in 12 to 15 months. The government got GM stock as part of a 2009 bailout.
Elsewhere on Wall Street, technology stocks and energy companies were among the early winners. Telecommunications companies and utilities fell the most in early trading.
Business software maker Oracle jumped $1.16 to $34.04 a share after reporting stronger earnings as companies splurged on software and other technology.
In the bond market, the yield on the benchmark 10-year U.S. Treasury note fell 0.02 percentage point to 1.80 percent.