China Unicom is forecasting a 50 percent increase in full-year net profit for 2012 on the back of strong growth in its 3G business.

“Due to the expansion of the 3G and broadband user base, the revenue of the company in 2012 had grown steadily and rapidly and the growth rate of the revenue had exceeded that of the costs and expenses of the company,” the Chinese number-two said in a statement this morning.

But it warned that the 50 percent increase in income was based on “preliminary calculations” and could differ from its fully audited 2012 results due in March.

Unicom announced earlier in this month that it added 3.1 million net new 3G subscribers in December 2012 alone, bringing its 3G total to 76.5 million – representing about 32 percent of its total customer base.

The operator’s 2G customer base was virtually flat at 162.9 million.