MetLife shares were at their lowest since December on Wednesdayas the company faces a possible S&P downgrade over theacquisition of a unit of American International Group Inc.

According to Reuters, MetLife shares dropped more than 4 percent, a dayafter the company confirmed it was discussing the possibility of acquiring AIG's American Life Insurance Company(Alico).

Shares were down $1.50 at $34.87 on the New York StockExchange.

MetLife's Chief Executive Robert Henrikson told Reuters in aconference call there is "no certainty" MetLife will reach a dealfor Alico.

"Management added on the call the company would not sell anycurrent businesses to finance a possible deal, nor would it usecapital in an off-shore reinsurance unit toward a deal," accordingto Reuters.

"We placed our ratings on MetLife on CreditWatch negativebecause of the sheer size of ALICO and to reflect our view that thepotential acquisition could have a material adverse impact onMetLife's financial metrics, such as capitalization andfixed-charge coverage, as well integration risks," said ShellieStoddard, an S&P credit analyst, in a statement.

S&P said MetLife's capitalization and financial flexibilityare below expectations for its rating, according to Dow Jones Newswires. S&P currently has the counterpartycredit rating at A-.

The MetLife/AIG deal could value at around $15 billion,according to reports.