The decline in global energy prices may prove a challenge to the credit quality and credit rating of Papua New Guinea's Bank of South Pacific. Standard & Poor's yesterday said it revised its long-term issuer credit rating on BSP to negative from stable. At the same time, S&P affirmed its B+ long-term and B short-term ratings on the bank.One of the consolidators in Pacific banking, BSP has a market share of around 55 per cent in PNG and assets of 17 billion kina.It most recently acquired Westpac's Samoa, Cook Islands and Tonga operations. In 2009 it purchased Commonwealth Bank's Fiji operations.The issues facing BSP relate to pressures on the PNG economy and the public sector businesses in particular that comprise a large part of its business.S&P said Papua New Guinea's financial institutions "face increasing risks stemming from increasing credit pressures on both the sovereign and broader operating environment as a result of lower global energy prices."On the other hand, it said it believed "important credit factors specific to BSP remain broadly unchanged, [but] we consider it unlikely that BSP would be insulated from increasing credit pressures on both the sovereign and the broader operating environment as falling export revenues increase the risk to the government's financials and the economy's external vulnerabilities."