NEW YORK (AP) - Stock fell Friday after China said for the second time in a month it would force banks to increase their reserve levels.

Chinese regulators are trying to contain rapid economic growth to prevent speculative investment bubbles there. The surprising move comes a day after a tame inflation report raised hopes that China wouldn't have to further tighten its monetary policy.

A similar action nearly a month ago by China spooked the market and helped start a selloff that brought major indexes down for four straight weeks.

Concerns about debt problems in European countries like Greece, Spain and Portugal, as well as President Barack Obama's push for new regulations on banks also weighed on the market and increased volatility in recent weeks.

On Thursday, European Union leaders pledged to provide Greece with support as it tries to bring its debt problems under control. There has been concern that debt problems there could spread and destabilize Europe's common currency, the euro.

In early morning trading, the Dow Jones industrial average fell 133.85, or 1.3 percent, to 10,010.34. The Standard & Poor's 500 index dropped 13.48, or 1.3 percent, to 1,064.99, while the Nasdaq composite index fell 23.12, or 1.1 percent, to 2,154.29.

A Commerce Department report that showed retail sales grew more than expected in January had little effect on trading. Retail sales rose 0.5 percent last month, slightly better than the 0.3 percent expected by economists polled by Thomson Reuters.

The report, which was delayed a day because major snowstorms shut down the federal government, was the best showing since November.

In corporate news, Warren Buffett's Berkshire Hathaway Inc. is being added to the Standard & Poor's 500 index. Funds created to mimic the movements of the S&P 500 will have to rebalance their portfolios to add Berkshire stock.

Stocks rose Thursday following announcements that European leaders would help Greece with its debt problems. Details of a rescue package are expected next week.

The Dow Jones industrial average jumped 1.1 percent Thursday, while the S&P 500 rose 1 percent and the Nasdaq composite index gained 1.4 percent.

With investors pulling out of riskier assets like stocks and commodities Friday, safe-haven investments like the dollar and Treasury bonds rallied.