Stocks retreated despite positive consumer spending and income reports, as investors worried over what President Barack Obama will do to punish Syrian President Bashar Assad's regime for using chemical weapons against civilians.
The Dow Jones industrial average lost 4.7 percent for the month, plunging from a record high of 15,499.54 at the start of the month. By the close Friday, the Dow had dipped 30.64 on the day or 0.21 percent to close at $14,810.31.
The Nasdaq dropped 30.43 points or 0.84 percent to 3,589.87, 30 points less than it was at the beginning of the month. The Standard & Poor's 500 lost 5.20 points or 0.32 percent to 1,632.97, down from its 1,685.73 finish July 31.
On the New York Stock Exchange 916 issues advanced while 2,113 declined on total volume of 3.125 billion shares.
In Asia Japan's Nikkei 225 index lost 70.85 points or 0.53 percent to close at 13,388.86 while the Hong Kong Heng Seng index gained 26.59 or 0.12 percent to 21,731.37. In Europe the London FTSE dropped 70.12 points or 1.08 percent to close at 6,412.93 while the German DAX lost 91.40 points or 1.12 percent to 8,103.15 and the French CAC 40 gave up 52.57 points or 1.32 percent to 3,933.78.
On currency markets the euro fell to $1.3222 and the dollar fell to 98.15 yen. On the Comex division of the New York Mercantile Exchange, Gold was off $18.10 to $1,394.80 per troy ounce and silver was off 60 cents to $23.54.
The 10-year U.S. treasury note fell 7/32 to yield 2.791 percent.
In after hours trading, crude oil was off $1.16 to $107.64 per barrel on the NYMEX.
On the Chicago Board of Trade, December corn was up 1 1/2 cents to $4.83 a bushel, November soybeans lost 11 cents to $13.57 1/2 a bushel and December wheat gained 1/4 cent to 6.54 1/2 a bushel.