Legislation passed two years ago in Florida, however, allows a reinsurer to post reduced collateral as long as it is highly rated and financially sound.

Moody's said the development in Florida "is part of an emerging trend by U.S. regulators at both the state and national level that has the potential to lower collateral requirements for foreign reinsurers when they operate in the U.S."

Moody's cited circular draft amendments in New York that are similar to the Florida rules.

Additionally, on the national level, the rating agency said the National Association of Insurance Commissioners (NAIC) has been trying to extend the concept to all states by pushing a federal legislative approach that would reduce reinsurance collateral requirements.

For reinsurers, the result would be reduced costs when doing business in the U.S. Moody's said that, according to U.S. insurance regulatory filings, non-U.S. reinsurers put up $23 billion in letters of credit as of year-end 2009 to meet the current collateral requirements.

For the bondholders, Moody's said, "While more collateral provides more security to policyholders and reinsurance buyers, that enhanced security comes at the expense of liquidity to the reinsurers' unsecured creditors, making this latest news an incremental positive for reinsurers' bondholders."

Risks may increase for buyers of reinsurance, though, Moody's said.

"The only losers may be reinsurance buyers, who will now have less security but may also receive a better price, and U.S. reinsurers, who may lose some competitive advantage," the rating agency said.