US STOCKS-Wall St trims gains as support mounts for U.S. action against Syria
* Obama to seek congressional authorization for Syria action
* Verizon and Microsoft fall after announcing major deals
* ISM Manufacturing index comes in ahead of expectations
* Indexes up: Dow 0.11 pct, S&P 0.43 pct, Nasdaq 0.68 pct
NEW YORK, Sept 3 (Reuters) - U.S. stocks advanced on Tuesday after U.S. President Barack Obama decided to seek congressional authorization before taking military action against Syria, a move that was likely to shelve any strike for at least several days.
Indexes pared initial gains, however, after comments from several congressional leaders indicated support for Obama.
Obama, during a meeting with congressional leaders at the White House, 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 U.S. wars in Iraq and Afghanistan.
Both John Boehner, the Republican speaker of the U.S. House of Representatives, and Eric Cantor, the House Republican majority leader, said they would support President Barack Obama's call for military action in Syria. Boehner urged his colleagues in Congress to do the same.
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.
"It's going to go up and down based on the expectations of when it is going to happen, but something is going to happen," said Uri Landesman, President at Platinum Partners in New York.
"You will see it trade down into the speculation and then once it actually happens, assuming it's not too big, you'll see a rally. Sell into the news, buy on the news, essentially."
Equities have recently been pressured by the prospect of a Western strike against Syria after chemical weapons were used to kill civilians, sending the S&P down 1.8 percent last week.
Congress returns from its summer recess on Sept. 9, and any vote to authorize a strike will come after that.
U.S. crude futures edged up 0.3 percent. Oil spiked 2.5 percent in August, largely driven by concerns that military action in the Middle East would disrupt crude supplies.
The Dow Jones industrial average rose 17.01 points or 0.11 percent, to 14,827.32, the S&P 500 gained 6.95 points or 0.43 percent, to 1,639.92 and the Nasdaq Composite added 24.317 points or 0.68 percent, to 3,614.185.
Verizon Communications agreed on Monday to pay $130 billion to buy Vodafone Group out of its U.S. wireless business, bringing an end to an often tense 14-year marriage. Verizon lost 2.7 percent to $46.10 while U.S. shares of Vodafone were flat at $31.45.
Nokia Corp agreed to sell its handset business to Microsoft Corp for $7.2 billion, sending its U.S. shares up 29.2 percent to $5.04 on record volume. Microsoft fell 6 percent to $31.40 as the biggest drag on the Dow.
In the latest economic data, the Institute for Supply Management's August manufacturing index came in at 55.7, above expectations for a reading of 54. July construction spending rose 0.6 percent, twice the rate that had been expected.
In addition, financial data firm Markit said while its final U.S. Manufacturing Purchasing Managers Index eased to 53.1 from July's reading of 53.7, a pickup in new orders and a drop in inventories pointed to faster growth ahead.
In the S&P, investors were watching the 100-day moving average at 1,639.42, which the index has been unable to close above since Aug. 26. Holding over that level would be a positive sign of near-term momentum.
CBS Corp on Monday reached an agreement with Time Warner Cable Inc to end a month-long blackout of its stations in New York, Los Angeles and Dallas. Financial terms of the deal were not disclosed. Shares of CBS rose 4 percent to $53.16 while Time Warner Cable added 1.6 percent to $109.02.