MetLife is paying $6.8bn in cash and $8.7bn in shares for American Life Insurance Company (Alico), which operates in more than 50 countries.
The announcement comes a week after AIG agreed to sell its Asian business AIA to UK group Prudential for $35.5bn.
AIG is seeking to repay $182.3bn of loans from the US government.
The sales of AIA, and now of Alico, have allowed AIG to make the first significant repayments of the emergency funding it received from the US government during the financial crisis.
AIG was given an initial $85bn in September 2008 to prevent its collapse at the height of the turmoil in the global credit markets, subsequently rising to $182.3bn. As part of its rescue, AIG became majority-owned by the US government.
AIG expects to raise $31.8bn in cash from the sales of Alico and AIA, which it can use to repay the government, including a $9bn investment in the company made by the Federal Reserve Bank of New York.
It will also receive shares and other securities as payment from Metlife and Prudential, which are currently valued at $19.2bn, and can be sold by AIG over time to raise further cash.
Mr Gifford added that one more sale by AIG may be in the pipeline, this time of its remaining Japanese assets to Prudential Financial Inc of the USA, which is a separate company from the UK’s Prudential group.