The U.S. once again may be emerging as a main engine for global growth — and at an opportune time, as Europe slides into recession and China's economy decelerates.

An improving job market, rising stock prices and easier credit are combining to lift U.S. consumer confidence and spending, with optimism measured by the Bloomberg Comfort Index near a four-year high. Personal-consumption expenditures increased by the most in seven months in February, rising 0.8 percent, the Commerce Department said last week.

"We're entering a sweet spot for the economy," said Allen Sinai, president of Decision Economics Inc. in New York. "We're in a self-reinforcing cycle," where faster employment growth leads to higher household income and increased consumer spending.