UPDATE 1-China Unicom Q3 pft weak, trend to continue

* Q3 profit down 11 pct qtr/qtr, margin pressure ahead

* Q1-Q3 ARPU slips to 41.6 yuan from 41.7 yuan in H1 (Recasts, adds details, background)

By Kirby Chien

BEIJING, Oct 30 (Reuters) - China Unicom (0762.HK), the country's No.2 mobile carrier, said profit declined from the previous quarter, a weakening trend that could continue as competition intensifies and expensive 3G networks are built.

Last week, rivals China Mobile (0941.HK), the world's No.1 mobile carrier, and China Telecom (0728.HK) also reported disappointing earnings. [ID:nPEK75764]

Unicom is building its 3G network with the world's most mature standard, WCDMA, but is struggling to integrate new businesses after last year's industry shakeup that saw it combined with another company to take on its current form.

Signing a three-year non-exclusive deal to sell Apple's (AAPL.O) popular iPhone will help the company's 3G launch, but the iconic handset is expensively priced and may eventually require more subsidies to achieve wider acceptance.

Unicom said on Friday that its third quarter net profit fell to 2.72 billion yuan ($398 million) based on Reuters calculations using data from the company's website.

That performance comes with Unicom a different company from what it was last year when Beijing restructured the industry, aiming to increase competition and nurture a domestic 3G standard.

Unicom is integrating a fixed-line network it absorbed in the revamp, while also building a 3G network after selling its CDMA mobile network to China Telecom.

Analysts were expecting Unicom to see a decline in margins for earnings before interest, taxes, depreciation and amortisation (EBITDA) in the quarter.

China International Capital Corp expected EBITDA margins to decline to 36 percent in the quarter from 38 percent in the previous quarter, it said before the results were announced.

Unicom's average revenue per user or ARPU, a common industry measure, slipped to 41.6 yuan in the third quarter from 41.7 yuan in first half, continuing a recent trend as carriers look to less affluent rural areas for growth iwith penetration rates in big cities high.

The three rival carriers have been under pressure since late last year when they initiated a $58.5 billion plan to build 3G networks capable of carrying more data and multimedia content to the world's largest wireless market. [ID:nPEK343905]

Unicom and its two rivals lagged the 8.16 percent gain on Hong Kong's China Enterprises Index .HSCE during the third quarter.

Only Unicom's shares rose in the quarter, up 7 percent, boosted by the promise of selling Apple's (AAPL.O) iPhone. China Mobile fell 2.6 percent and China Telecom lost 5.2 percent.

Unicom is integrating a fixed-line network it absorbed in the revamp, while it is also building a 3G network after selling its CDMA mobile network to China Telecom. ($=6.83 yuan) (Reporting by Kirby Chien; Editing by Chris Lewis)