Saudi shares dropped 5.5 percent to their lowest close in nearly five months, weighed by petrochemical and banking shares, after S&P downgraded the United States\' credit rating. The United States lost its top-tier AAA credit rating from Standard & Poor\'s on Friday in an unprecedented blow to the world\'s largest economy in the wake of a political battle that took the country to the brink of default.\"The market is being hit by the action of Standard and Poor\'s,\" said Saudi economist Abdulwahab Abu Dahesh.The index of the largest Arab bourse fell to 6,073 points, its lowest close since March 16, after suffering its biggest daily decline since March 1.The benchmark has lost 8.3 percent this year.The petrochemical index tumbled 6.7 percent and the banking index dropped 4.7 percent. \"The Saudi market is strong ..., but it is correlated to US debt and debt in Europe and how it is handled,\" Abu Dahesh said, adding that the bourse may see fluctuations in the coming week.Petrochemical giant Saudi Basic Industries Corp (SABIC) lost 5.8 percent and heavyweight Al-Rajhi Bank fell 5.2 percent. From / Arabian Business News