The world's private sector economy picked up speed in December, expanding at its fastest rate in nine months thanks partly to an upturn among U.S. companies, a business survey showed on Thursday.

JPMorgan's Global All-Industry Output Index rose to 53.0 in December from 52.0 in November, comfortably above the 50 mark that divides growth from contraction and suggesting steady global economic growth.

Survey compiler JPMorgan said the United States was the main factor driving the global economic expansion in December, while businesses also picked up the pace in the UK, India and Brazil. The euro zone, however, remained a laggard last month.

The services index also hit a nine-month high in December, rising to 53.2 from 52.7, although employment in services industries fell slightly for a second successive month.

(Reporting by Andy Bruce; Editing by Toby Chopra)