Global stocks gained for a 10th day, sending the MSCI World Index to its longest rally in 11 months, oil and copper soared and Treasuries retreated after China said it will relax the yuan’s fixed rate to the dollar.

The Standard & Poor’s 500 Index rose 0.7 percent and the Stoxx Europe 600 Index climbed to the highest level since May 13 at 11:05 a.m. in New York. The MSCI Asia Pacific Index jumped 2.5 percent, the most in more than two weeks. Oil exceeded $78 a barrel and copper rallied to lead gains in commodities. The Korean won strengthened as the yen and dollar fell against most major currencies, while the 10-year Treasury yield surged 5 basis points to 3.27 percent.

Stocks rallied from Tokyo to New York after the People’s Bank of China said it will end a two-year currency peg adopted during the global financial crisis to protect exporters, a sign policy makers expect the world economy to strengthen. China, the world’s largest copper consumer and second-biggest user of oil after the U.S., signaled the change before the G-20 summit in Toronto on June 26 to 27.

“China’s move is a positive,” said Burt White, who helps oversee $284 billion as chief investment officer at LPL Financial Corp. in Boston. “It’s going to help exporters in the U.S. and Europe. It shows that China and the U.S. will continue to be the two main engines of growth. Commodities are pricing in a strong advance in the global economy. The stock market has good momentum.”

Commodity Producers, Industrials

The S&P 500 rose for a third day, its longest rally in two months. Commodity producers and industrial companies led the advance. Caterpillar Inc., Alcoa Inc. and General Electric Co. rallied at least 2.3 percent to lead gains in the Dow Jones Industrial Average.

The People’s Bank of China pledged on June 19 to make the yuan more flexible, while ruling out a one-time revaluation of the currency that’s been held at about 6.83 yuan per dollar since mid-2008. The global economy is “gradually recovering and the upturn in the Chinese economy has become more solid,” it said in a statement announcing the action.

“This decision is great for industrial, energy and materials stocks,” said Don Wordell, a fund manager for Atlanta-based RidgeWorth Capital Management, which oversees about $62 billion. “You will have rising demand from China because oil is getting cheaper to the Chinese consumers, industrial companies will have to build out the energy infrastructure and materials producers will benefit from higher wages and wealth in China.”