China Mobile, the world's largest mobile carrier, faces a further squeeze on profit margins as competitive pressures intensify and an expensive buildout of a new 3G network weighs.

The firm, which had 493 million users at the end of June, yesterday posted its slowest interim profit growth since it listed in 1997 and said it expects average revenue per user (ARPU), a key barometer of earnings, to slide in the months to come.

Like smaller rivals China Unicom and China Telecom, which now compete with a full range of services after a major restructuring last year, China Mobile is aggressively moving into rural areas as urban markets become saturated.