Legendary investor, Warren Buffett — the Sage of Omaha — in a move he says is designed to make money, has offered to take on $800 billion of the liabilities of U.S. municipal bonds.

The offer goes to three “monoline” bond insurers, Ambac Financial, MBIA and Financial Guaranty Insurance. One has already rejected the deal, and he is still awaiting reponses from the other two, although one of them is making favourable noises.

The move breathed new life into global stock markets yesterday. The monolines are seen as the second line of defence against the sub-prime mortgage fiasco by propping up banks’ balance sheets in the event of a repayment meltdown.

Traditionally, the bond insurers concentrate on municipal risk, but they too got caught up in the collective madness of sub-prime lending for the same reason respectable banks did : greed for perceived easy money.

However, the monolines are now short of capital and are being hit by downgrades from the rating agencies.

T J Marta, fixed income strategist at RBC Capital Markets, said it was a coup for bond insurers, which could help them avoid “the doomsday scenario”.