By Ryan Vlastelica

NEW YORK (Reuters) - U.S. stocks closed sharply higher on Monday, with the Nasdaq ending at its highest level since September 2000, as upbeat data from China boosted optimism about the health of the global economy.

Sentiment was also lifted by merger activity and easing concerns about a potential Western-led strike on Syria.

The S&P 500 closed higher for a fifth straight sessions, posting its best daily performance since August 1, while all 10 S&P sectors ended higher. More than 70 percent of companies that trade on both the New York Stock Exchange and Nasdaq rose.

Basic materials shares (.SPLRCM) led the day's gains, rising 1.5 percent, after China's August exports handily beat market expectations while consumer inflation held steady. U.S. Steel Corp (NYS:X) jumped 3.5 percent to $19.53 while Alcoa Inc (AA) rose 2 percent to $8.08.

"This is more proof that the Chinese government's attempts to stabilize the country's economy are helping, and that really got us up and running," said Donald Selkin, chief market strategist at National Securities in New York.

Equities added to their gains in afternoon trading as it appeared less likely that a resolution authorizing military strikes against Syria would easily pass the U.S. legislature. Geopolitical uncertainty related to Syria has been a major market driver in recent weeks, with investors especially concerned about the potential impact on the oil market.

U.S. Senate Democratic Leader Harry Reid set a test vote for later this week, but it was unclear whether the measure would attract enough backing to clear anticipated procedural roadblocks.

"Every poll shows it would be very difficult for Obama to get authorization, and that might be enough to delay any action or at least make the action more cautious," said Selkin, who helps oversee $3 billion in assets. "Both of those would give the market a leg up."

Separately, a Russian proposal to place Syria's chemical weapons under international control was welcomed by the government in Damascus, which praised the Kremlin for seeking to "prevent American aggression.

The Dow Jones industrial average (.DJI) was up 140.62 points, or 0.94 percent, at 15,063.12. The Standard & Poor's 500 Index (^GSPC) was up 16.54 points, or 1.00 percent, at 1,671.71. The Nasdaq Composite Index (.IXIC) was up 46.17 points, or 1.26 percent, at 3,706.18.

The S&P rose above its 50-day moving average for the first time since August 23, a sign of positive near-term momentum. The index has risen for five straight sessions, up 2.4 percent over that period.