Chief executives expect the U.S. economy to continue its slow, uneven recovery over the next few months and are concerned about the rising costs of raw materials and the expense of complying with regulations, according to a survey released on Wednesday.

One in four CEOs polled by the Business Roundtable cited materials as their main cost worry, followed by the cost of complying with regulations, which worried 24 percent.

There are old fashioned regular business pressures. Commodity prices, oil prices, challenges with health care costs, said James McNerney, CEO of Boeing Co , who serves as chairman of the Roundtable.

The group's quarterly CEO Economic Outlook index was little changed. It inched up to 77.9, from 77.6 in the third quarter. Any number above 50 represents growth. They estimated real U.S. gross domestic product would rise 2 percent next year.

We continue to see strengthened fundamentals in American business but it's combined with an uneven and slow recovery and reflects continued uncertainty by CEOs over the next six months, McNerney said on a conference call with reporters.

We're right at the point where the economy is growing but not enough to offset productivity and create jobs, McNerney said.

Of the Business Roundtable CEOs polled, 35 percent said they expected to add jobs in the United States over the next six months, down from 36 percent who expected that in October. Sixty-eight percent expected their companies' sales to rise in the next six months, up from 65 percent last quarter.

Corporate America has taken a cautious but generally positive view of 2012, despite the worries posed by the European debt crisis. General Electric Co on Tuesday forecast double-digit percentage growth in profit next year, and DuPont said earnings per share could rise 12 to 17 percent next year.

The Roundtable, which represents businesses that collectively generate $6 trillion in annual revenue, surveyed its members between October 31 and November 18.

(Reporting by Scott Malone in Boston, editing by Dave Zimmerman and Gerald E. McCormick)