Concerns about a slowdown in the U.S. economy sent the Standard & Poor's 500-stock index to its sixth straight day of losses, its longest such streak since February 2009, as investors continued to worry that the recovery has run out of steam. The Dow Jones Industrial Average fell 21.87 points, or 0.18%, to 12048.94, its sixth straight loss and longest slide since July of last year. The S&P 500 finished 5.38 points lower, or 0.42%, at 1279.56, as materials and financial stocks dragged. The Nasdaq Composite dropped 26.18 points, or 0.97%, to 2675.38. The Dow Jones Transportation Average, which hit a record high in May, lost 58.62, or 1.14%, to 5088.48 to turn negative year to date.

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Concerns over the outlook for the U.S. economy have dominated investor sentiment for weeks, and investors took little heart from the Federal Reserve's most recent Beige Book, in which businesses said the economy expanded over the past two months. Caterpillar and Alcoa fell 1.8% to lead the blue-chip Dow lower, followed by American Express, which lost 1.6%. Verizon Communications led blue-chip gainers, rising 1.5% after Oppenheimer & Co. upgraded its investment rating on the stock with predictions of solid growth in cloud, or remote, computing and gains in wireless market share. Exxon Mobil also helped keep the Dow's losses in check, pushing 1% higher after lower than expected U.S. oil inventories and after the Organization of Petroleum Exporting Countries said members were unable to reach a consensus on boosting oil production.

European stock markets dropped sharply Wednesday, hit by renewed concerns over Greece's debt situation as well as comments on U.S. economic growth by Federal Reserve Chairman Ben Bernanke. The Stoxx Europe 600 index fell 1.1% to end at 269, posting its sixth straight losing session. Peripheral markets suffered steep losses. In Greece, the ASE Composite index was particularly hard hit, falling almost 3%, as shares of Alpha Bank AE dropped 7.7%. The losses came after German Finance Minister Wolfgang Schaeuble sent a letter Tuesday to euro zone members insisting that private holders of Greek bonds share the pain of a new aid program by agreeing to a swap that would stretch the maturity of Greek sovereign bonds by seven years. Banks stumbled across Europe, hit by growth worries in the U.S. but also by Greece as many European lenders, especially some French and German banks, have exposure to Greek debt. Deutsche Bank AG and Societe Generale SA both fell 1.4%. The Italian FTSE MIB index fell 1.4%, with Banca Monte dei Paschi di Siena SpA shares down 3.1%. Portugal's PSI 20 index was down 1.7%, with Banco Comercial Portugues SA 3.9% lower. In London, shares of Antofagasta PLC sank 5% after the miner said that the ramp up of its Esperanza mine in Chile was taking longer than initially expected. Other mining stocks also fell, with Fresnillo PLC losing 2.4%. The FTSE 100 index fell 1% to 5,808.89, led down by Antofagasta. In Paris, shares of telecom-equipment group Alcatel-Lucent fell 3.3%, weighing on the CAC 40 index which closed down 0.9% at 3,837.98. Shares of retailer Carrefour SA declined 1.9%. The German DAX 30 index ended 0.6% lower at 7,060.23, led down by Infineon Technologies AG, which dropped 2.5%. In Helsinki, Nokia Corp. shares dropped 4.2% after bid speculation, extending recent declines after last week's profit warning.

Asian share markets ended mostly lower Wednesday as comments from Federal Reserve Chairman Ben Bernanke did little to assuage worries about U.S. economic growth for investors also fretting about the possibility of further tightening by China. The Hang Seng index lost 0.9% to 22661.63 even as the Shanghai Composite index eked out some late gains to end 0.2% higher at 2750.29. The Nikkei Stock Average index also managed to rise 0.1% to end the session at 9449.46, but South Korea's Kospi index declined 0.8% to 2083.35, India's Sensex lost 0.6% to 18394.29, and Singapore's Straits Times Index fell 0.4% to 3102.98. In Hong Kong, banking giant HSBC Holdings declined 0.9%, while oil firm CNOOC fell 0.2% on a fall in light, sweet crude futures. South Korean shares were under notable selling pressure, with Hyundai Motor down 2.7%. The Bank of Korea revised downward the first-quarter gross domestic product, saying it was up 1.3% from a year earlier, rather than the earlier estimate of 1.4%. Japanese car makers were mixed, with Honda Motor ending the day down 1.3% but Toyota Motor rising 0.2%. Sony shares managed to gain as well, rising 0.3% and paring week to date losses to 4.3%. However, Tokyo Electric Power dropped 7.4%. Other utilities were also pressured, with Kansai Electric Power Co. down 0.7%, and Chubu Electric Power Co. 2.1%.

Copper on the London Metal Exchange closed Wednesday's open outcry session 1.2% lower after a slump in the euro and world equity markets. The decline followed downbeat comments by Federal Reserve Chairman Ben Bernanke late Tuesday, which weighed heavily across financial markets throughout the session. A drop in German exports and disappointing industrial production data Wednesday meanwhile cast a shadow of doubt on the strength of the recovery in Europe's largest economy. Reports that the strike at Chile's El Teniente could be resolved soon didn't help copper prices. The red metal did, though, manage to hold above the key price of $9,000 a metric ton, finishing the PM kerb at $9,030/ton. Volumes were also thinner, and other base metals closed mixed, as investors eyed a meeting of the European Central Bank Thursday. Oil futures surged above $100 a barrel Wednesday after the Organization of Petroleum Exporting Countries said it would leave production quotas unchanged. Light, sweet crude oil for July delivery settled up $1.65, or 1.7%, at $100.74 a barrel on the New York Mercantile Exchange. Brent crude oil on the ICE futures exchange, which has held above $100 since February, settled up $1.07, or 0.9%, at $117.85 a barrel. OPEC's decision came as a surprise to oil-market participants, who had widely expected the group to boost its output ceiling in response to triple-digit oil prices and projections for robust economic growth in the second half of the year. Gold and other precious metals futures fell, held back by a rise in the dollar against the euro as worries about European debt grip investors. The most actively traded gold contract, for August delivery, fell $5.30, or 0.3%, to settle at $1,538.70 a troy ounce on the Comex division of the New York Mercantile Exchange. Silver for July delivery, the most actively traded contract, fell 1.2% to settle at $36.620 a troy ounce.

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