A private research group says its forecast of future economic activity jumped 1.1 percent in December, suggesting that economic growth could pick up this spring.
The increase in the Conference Board's index of leading economic indicators was larger than the 0.7 percent rise that economists had expected.
The gauge had risen 0.7 percent in November and has been up for nine consecutive months.
Eight of the 10 components in the index showed improvement in December.
Some economists have been worrying that growth in the economy will stagnate this year as government support programs wind down and unemployment remains high.
The leading indicators index is designed to forecast economic activity in the next three to six months.