Manufacturers in the U.S. are more optimistic about sales and spending next year than service providers, signaling that factories will support the economic expansion after they slumped in recent months, according to a survey by the Institute for Supply Management.

Purchasing managers at U.S. factories anticipate sales will grow 4.6 percent in 2013 and business investment will increase 7.6 percent, the Tempe, Arizona-based group’s forecast showed Tuesday.

By contrast, service providers estimate revenue will grow 4.3 percent next year and that capital spending will rise 7 percent, the ISM said.