S&P Global Ratings has revised its outlook on AMP Bank Ltd from stable to negative. The revision to a negative outlook on AMP Bank reflects the potential downward rating pressure on the AMP group's credit profile - as reflected in negative outlooks from S&P on AMP Ltd and AMP Group Holdings Ltd (AGHL), which guarantees the bank's liabilities."In our view, the bank's credit profile benefits from both explicit support, in the form of a guarantee from AGHL, and implicit support from the wider group if needed because we consider the bank to be a strategically important subsidiary of the group," S&P's analysts observed in a note explaining the revised outlooks for AMP Bank."We expect to lower our rating on AMP Bank in the next two years if both of the following occur: we formed an opinion that the creditworthiness of the AMP group has weakened, and we downgrade AGHL."At the same time, S&P affirmed its 'A' long-term and 'A-1' short-term issuer credit ratings for AMP Bank.