NEW YORK (AP) — US stocks opened lower Monday, led by declines in energy stocks as the price of oil plunged again. The euro sank to a nine-year low against the dollar as new doubts surfaced about Greece's future in the common currency bloc.

KEEPING SCORE: The Standard & Poor's 500 index dropped 17 points, or 0.8 percent, to 2,041 as of 9:48 a.m. Eastern. The Dow Jones industrial average fell 132 points, or 0.7 percent, to 17,705. The Nasdaq composite dropped 31 points, or 0.7 percent, to 4,695.

ENERGY: Oil prices extended a slide that began in June last year. Benchmark U.S. crude was down $1.91 at $50.76 a barrel on the New York Mercantile Exchange. The contract dropped 58 cents to $52.69 on Friday. Oil is down from $107 a barrel in June as global demand slackened while supplies remained high.

Energy stocks led declines in the S&P 500, dropping 1.9 percent. Chevron fell $2.5, or 2.2 percent, to $110.11 and Exxon Mobil dropped $1.43, or 1.5 percent, to $91.41.

EURO JITTERS: The euro was trading at $1.1922 after falling to $1.1862, its lowest since December 2005. The drop was triggered by reports that German Chancellor Angela Merkel no longer believes it would be too risky for the 19-member eurozone if Greece dropped out of the currency bloc. Upcoming elections in Greece could be won by the Syriza party which wants to renegotiate the terms of the country's international bailout, threatening its place in the euro group of countries.

The euro has also been under pressure from expectations that the European Central Bank will expand monetary stimulus as the region's economy struggles.

EUROPEAN STOCKS: In stock market trading, France's CAC 40 was down 2.1 percent and Germany's DAX was 1.7 percent lower. Britain's FTSE 100 shed 1 percent.

BOND PRICES: In U.S. government bond trading, prices rose. The yield on the benchmark 10-year Treasury note, which falls when prices rise, dropped to 2.07 percent.