U.S. services firms expanded at a solid but much slower pace in December compared with the previous month, a sign growth may have cooled at the end of last year.

The Institute for Supply Management says its services index fell to 56.2 last month, down from 59.3 in November. Yet the drop comes from a very high level: November's reading was near an eight-year high of 59.6 reached in August. Any reading over 50 indicates expansion.

A measure of sales fell sharply and a gauge of orders also declined. But growth in hiring was just slightly below November's reading, suggesting that job gains last month were still healthy.

The government releases December's jobs report Friday.