Standard and Poor's raised China's long-term sovereign credit rating on Thursday, based on the government’s efforts in bank reforms and economic liberalization, Reuters reported.   Standard and Poor’s said that the outlook is stable. The long-term sovereign rating is upgraded from A- to A.   'The upgrade on the ratings on China reflects its persistent efforts to strengthen the banking sector that will reduce the future fiscal burden, as well as China's continuing economic liberalization and reform that will further entrench excellent growth prospects,' quoted Ping Chew, a credit analyst with Standard & Poor's sovereign ratings group.   Andrew Freris, chief Asia-Pacific economist for BNP Paribas, said the upgrade was no surprise given that China has a huge external surplus and is a booming economy with low inflation, quoted Reuters.   "The most important thing is China's external debt is around $318 billion and they have foreign exchange reserves of $941 billion. China is a net lender to the world to the tune of $623 billion -- primarily to the U.S.   Howeverm Standard and Poor's noted htat monetary policy has so far been constrained by structural rigidities, including China's exchange rate and use of investment as a key driver of growth.