Bailed-out insurer American International Group took another step toward winding down its U.S. government support on Monday by securing $4.3 billion of bank credit lines, and company shares surged.

AIG's shares closed up 9.3 percent, or $5.05, to $59.38 on the New York Stock Exchange. The price was a two-year high for the stock, which was posting its largest one-day gain since rising 12 percent on December 9.

AIG and its property insurance unit Chartis Inc agreed to three separate credit facilities with banks, partially replacing credit lines from the Federal Reserve Bank of New York, AIG said in regulatory filings.

We believe we are close enough to completing our recapitalization plan that we can see the finish line, said Robert Benmosche, AIG's chief executive, in a prepared statement.

JPMorgan Chase & Co, Bank of America Corp, and Citigroup Inc were joint lead arrangers for the three facilities. AIG said in a prepared release that 36 banks agreed to participate in the credit facilities.

AIG signed two credit agreements worth $1.5 billion each, one for three years and another for 364 days, it said in a regulatory filing.

Separately, Chartis signed a $1.3 billion letter of credit and reimbursement agreement with its lenders.

The new credit facilities will be used once the previously announced recapitalization plan with the U.S. Treasury Department and the New York Fed is closed, effectively ending a portion of the government's support of the insurance giant issued at the height of the financial crisis in the fall of 2008.

The new private sector credit line is not a dollar-for-dollar replacement of the Fed's credit line, which currently totals $21 billion.

But the Fed's credit line is expected to be paid off in the first quarter 2011, according to the insurer's previously announced recapitalization plan.

In total, the U.S. government holds a $91 billion stake in AIG.

The facilities come less than a month after the insurer returned to the debt market after a two-year absence, raising $2 billion in unsecured notes.

(Reporting by Joe Rauch in Charlotte, North Carolina and Archana Shankar in Bangalore; Editing by Gopakumar Warrier, Dave Zimmerman, and Carol Bishopric)

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