US stocks closed sharply lower Thursday after the head of the European Central Bank poured cold water on hopes that the bank will boost its bond-buying to help contain the eurozone debt crisis. The blue-chip Dow Jones Industrial Average tumbled 195.72 points (1.60 percent) to 12,000.65 in closing trade. The broader S&P 500 lost 26.32 points (2.09 percent) to 1,234.69, while the Nasdaq slid 52.52 points (1.98 percent) to 2,596.69. \"Comments from European Central Bank president Mario Draghi cooled hopes that the central bank will step up its bond-buying efforts,\" Charles Schwab analysts said in a client note. Leaders of the 27-nation EU opened a crucial two-day summit in Brussels Thursday night mired in divisions over a treaty change demanded by Germany and undermined by an ECB warning there will be no big boost in rescue funding. Earlier the ECB cut its key interest rates for the eurozone, by a quarter of a percentage point to 1.00 percent. After the rate cut, ECB chief Mario Draghi said at a news conference that governments must to \"do their utmost\" to resolve the crisis and restore confidence in the euro. \"The ultimate decisions are in the hands of leaders,\" Draghi said.