Stocks were poised to rally at the open on Monday as China's vow to allow a flexible yuan invigorated optimism in the global recovery and raised the outlook for sales in the long term at U.S. multinationals.

China's yuan surged the most since its revaluation in 2005 following the surprise weekend announcement by China's central bank that it would allow greater flexibility for the currency.

The move is expected to boost purchasing power and demand in China, the world's third largest economy. A higher yuan would also help temper inflation by pushing down import prices, which could mean Beijing would have less need to tighten monetary policy aggressively.

Shares of multinationals Caterpillar Inc and Freeport-McMoRan Copper & Gold Inc gained in premarket trading. Caterpillar rose 1.9 percent to $67.10, while Freeport was up 2.8 percent at $68.41.

Wall Street was set to gain about 1 percent at the open, while world stocks hit a five-week high. Commodities prices jumped and oil futures rose more than 1 percent to $78.30 a barrel.

China's currency move raises the veil and reveals an improving global economic picture, said Andre Bakhos, director of market analytics at Lek Securities in New York.

It adds confidence that China's growth will start to be realized in other economies.

S&P 500 futures were up 14.1 points and above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures jumped 135 points, and Nasdaq 100 futures advanced 22.5 points.

The S&P 500 could find technical resistance near the 1,130 level, the midpoint between its 2010 high- and low-points and a key technical retracement. Above that, the benchmark faces a hurdle at its 50-day moving average, now at about 1,139. The S&P 500 closed at 1,117.51 on Friday.

An internal BP Plc document released by a U.S. lawmaker estimated that a worst-case scenario rate for the Gulf of Mexico oil spill could be about 100,000 barrels per day, far higher than the current U.S. government figure. BP's U.S.-listed shares slid 2.9 percent to $30.53.

Dell Inc is in talks with Google Inc over the use of Google's Chrome operating system on its laptops, a top Dell executive said. Dell trimmed some earlier gains to rise 0.5 percent to $14.11.

Stocks ground higher in another lightly traded session on Friday, ending a nervous week with gains despite signs of economic weakness at home and worries about public debt troubles in Europe.

(Additional reporting by Rodrigo Campos; Editing by Padraic Cassidy)