Futures sharply higher as potential Syria action delayed

U.S. stock index futures were sharply higher Tuesday, after positive global PMI (purchasing managers' index) data and as President Barack Obama opted to seek congressional authorization for military action against Syria.

U.S. markets were closed Monday for the Labor Day holiday.

Congress will hold its first public hearing about U.S. plans for military intervention in Syria as President Barack Obama seeks to convince skeptical Americans and their lawmakers about the need to respond to last month's alleged gas attack outside Damascus.

Obama struggled to win over skeptical lawmakers from both parties over the weekend, and congress will now only debate a strike when it returns from its summer recess on September 9.

On Monday, Verizon said it will pay $130 billion to acquire Vodafone's 45-percent stake in their Verizon Wireless joint venture, marking the third-largest deal in corporate history.

Vodafone's CEO told CNBC that he will use the cash earned from the deal to accelerate investment in Vodafone's own wireless networks, and to return $84 billion in cash and shares to shareholders.

(Read more: Vodafone CEO: We will spend cash pile on our networks)

"We are fortunate enough that the size of the deal itself allows us to return a large percentage to shareholders. But even the remaining 21 percent is large enough to strengthen the company and to allow us to accelerate our strategy," CEO Vittorio Colao said.

And Microsoft said it will buy Nokia's handset business for $7.2 billion. Nokia CEO Stephen Elop, a former Microsoft executive, will rejoin the company and is now seen by some as a candidate to replace retiring CEO Steve Ballmer.

On the economic front, the Institute for Supply Management will release its manufacturing sector data for August at 10 am ET. Analysts polled by Reuters expect the main index to slip to 54 from 55.4 last month. July construction spending is also scheduled for release at 10 a.m., and is expected to gain 0.3 percent.

The Japanese Nikkei led Asian stocks higher on Tuesday, after better-than-expected manufacturing data from Europe and China lifted hopes that a global economic recovery was in progress.

Data out on Monday showed Chinese manufacturing hit a four-month high in August and euro zone factory activity rose at its fastest pace since May 2011. On Tuesday, data revealed that the U.K.'s construction sector expanded at its fastest pace in almost six years in August.