NEW YORK (Bloomberg) — Standard & Poor's said its insurance ratings on MBIA Inc., the largest bond guarantor, probably won't be affected by its downgrade of Bermuda-based Channel Reinsurance Ltd. to a non-investment grade.

S&P cut Channel Re, whose business all comes from Armonk, New York-based MBIA, to BB+ from AA-, and then withdrew the grade at the company's request, the ratings company said in a statement yesterday. The "margin of safety" for the BBB+ rating on MBIA's insurance unit, which is under review for a downgrade, is "strong" even including losses related to the reinsurer, New York-based S&P said in a separate statement.