"The market got oversold last week and it needs to rally back some, but we won't see any gains as long as we have this overhang of military action," said Keith Bliss, senior vice president at Cuttone & Co.



During a meeting with congressional leaders at the White House, President Barack Obama called for a prompt vote on Capitol Hill and reiterated that the U.S. plan would be limited in scope and not repeat the long wars in Iraq and Afghanistan.

House Speaker John Boehner said he would support Obama's call for military action in Syria and urged his colleagues in Congress to do the same. Stocks came off their initial highs in midday trading following Boehner's remarks.

Nancy Pelosi, Democratic leader in the House of Representatives, said she believes Congress will support a resolution authorizing the use of U.S. military force against Syria.

(Read more: If US bombs Syria,here's how high oil could go)

Meanwhile, a Russian news agency reports that two "ballistic objects" had been launched towards the eastern Mediterranean revived concerns about a U.S.-led strike on Syria. Israel's Ministry of Defense confirmed that Israeli forces and the U.S. Missile Defense Agency had carried out a missile test and said Israel would release further information about the launch soon.

Apple gained after the tech giant issued an official invitation for an event on Sept. 10. Analyst widely expect the company to unveil a new iPhone.

On the M&A front, Verizon announced on Monday 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)