Retail sales in the US were unexpectedly flat during the December holidays, suggesting a pullback among consumers and raising questions about a broader economic slowdown.

The report, released on Tuesday by the Commerce Department, marks a break from relatively robust spending in recent months. Americans had continued to open their wallets even as sentiment about the economy dimmed.

But a faltering labour market, persistent inflation and cooling wage growth contributed to a lacklustre end to the year. Retail sales were unchanged from the previous month, after a 0.6% increase in November.

Still, economists cautioned that the weak December data might not point to a sustained downturn.

The data, which had been delayed because of last year's government shutdown, comes amid a slew of upcoming economic releases, including a report on the labour market on Wednesday and fourth-quarter economic growth estimates next week.