The surprise announcement Friday that the government will auction off its 14.4 million Chrysler Corp. warrants came after Shearson/American Express made an unsolicited offer to buy the warrants, Shearson executives disclosed this weekend.

Shearson Senior Vice President Paul J. Mejean said his firm delivered its offer Friday, apparently forcing the hand of Treasury Secretary Donald T. Regan, who a few hours later said the warrants would be sold to the highest bidder.

Mejean would not say how much Shearson offered for the warrants, but said the price is linked to the price of Chrysler stock and is higher than the going price for publicly traded Chrysler warrants, which closed Friday at 18 1/4.

Each Chrysler warrant gives the owner the right to buy one share of Chrysler for $13 a share, or less than half the $28 1/8 they sold for Friday on the New York Stock Exchange.

The government's warrants are expected to be worth more than those already in public hands because they are good until 1990 while the others expire in 1985.

The government got the warrants from Chrysler as a condition for providing the loan guarantees that enabled the auto company to avoid bankruptcy. The warrants were supposed to provide a way for the government to profit from the Chrysler bail-out.

Chrysler earlier this year asked the government to give the warrants back. When that offer was rebuffed, the company offered to buy them for $17.36 a share, a total of just under $250 million, but that bid also was rejected as inadequate.

In a statement, Chrysler Chairman Lee A. Iacocca said he was "shocked" by the decision to auction the warrants and complained that the government had "decided to go for the last $2 of profit."

Other Wall Street investment firms are expected to join Shearson/American Express in bidding for the warrants, which were virtually worthless when issued because Chrysler stock was selling for $5 a share.