Wall Street posts worst day since June on Syria concerns

NEW YORK (Reuters) - Wall Street stocks suffered their worst day since June on Tuesday, slumping in a broad decline as geopolitical uncertainty rose over a possible U.S.-led military strike by the West against Syrian President Bashar al-Assad's forces.

The S&P 500 closed under its 100-day moving average for the first time since June 24, a sign of weak near-term momentum. The day's fall extended recent declines on uncertainty over when the U.S. Federal Reserve will start to slow its stimulative monetary policies.

Odds grew that a strike would occur against al-Assad's forces for a chemical weapons attack against civilians as a number of nations and groups - including Britain, France, Canada and the Arab League - joined Washington in urging a firm response to Assad. Adding to the tension, Russia has supported Assad Syria's civil war.