Fears about a European debt crisis with potentially catastrophic consequences have weighed on markets since the spring. Economic data are mostly weak. Major stock indexes have fallen more than 10 percent. The Standard & Poor's 500 index is down 12 percent -- the most since the final quarter of 2008.
The government reports before the market opens on consumer spending and personal incomes in August. Economists expect spending edged up after rising in July.
At 7:33 a.m. Eastern time, S&P 500 futures were down 14, or 1.2 percent, at 1,143. Dow futures were down 118, or 1.1 percent, at 10,981. Nasdaq 100 futures were down 22, or 1 percent, at 2,168.