CHRISTOPHER S. RUGABERWASHINGTON (AP) â¿¿ Companies are holding off on purchases of computers, industrial equipment and other long-lasting manufactured goods, a trend that's slowing the U.S. economy. A fourth straight month of lackluster corporate spending led many economists on Thursday to trim their forecasts for growth in the July-September quarter. The government will issue its first estimate of third-quarter growth Friday, the last snapshot of overall economic activity before the presidential election. The troubling report on business confidence overshadowed a drop in applications for unemployment aid and a slight increase in the number of people who signed contracts to buy homes. Orders for durable goods, products expected to last at least three years, rose 9.9 percent in September, the Commerce Department said. But most of the increase was driven by a spike in aircraft orders, which are volatile and plummeted in the previous month. Economists pay closer attention to core capital goods, which include machinery and computers but exclude aircraft. Those orders were unchanged in September after only a slight gain in August and steep declines in July and June. And shipments of those goods fell for the third straight month. That means business spending on equipment and software likely declined 4.9 percent in the July-September quarter, economists noted. It would represent the first drop in that category since the recession. Corporate investment helped the U.S. economy emerge from the Great Recession three years ago. But businesses have grown more cautious since spring, seeing tepid growth in consumer spending and declines in exports. Many companies are worried that their overseas sales could dampen further if recession spreads throughout Europe, as some predict, and growth continues to slow in China, India and other developing countries. Businesses also fear large tax increases and big government spending cuts that will kick in next year if Congress fails to reach a budget deal to avert them.