WASHINGTON — The Treasury Department said Wednesday that a sale of MetLife stock by American International Group brought in $6.3 billion, which will go toward repaying a portion of the taxpayer bailout of the insurance company.

Treasury said that the $6.3 billion in gross proceeds from the sale would be used to redeem part of Treasury’s $18.2 billion investment in preferred equity shares in AIG.

AIG offered 146.8 million shares of its holdings in MetLife for sale at $43.25 a share.

The MetLife stock sale is part of the government’s effort to wind down its largest and most complex rescue from the 2008 financial crisis, when it assembled a $182 billion package to save AIG.

The government owns more than 1.6 billion shares of AIG common stock, giving it a 92 percent stake in the company. The Treasury is expected to start selling those shares in March.

Tim Massad, Treasury’s acting assistant secretary for financial security, labeled AIG’s sale of its MetLife holdings evidence of a “remarkable turnaround” for AIG.

“We are optimistic about the prospects that taxpayers will recover every dollar invested in AIG — something that many thought would be impossible when these investments were first made,” Massad said.

The stock sale weighed on MetLife’s stock Wednesday. Shares in the New York-based life insurer ended down $2.63, or 5.7 percent, at $43.41.