PetroChina Co will "bear the brunt" of a resource tax that is being expanded to 12 western provinces, reducing the largest Chinese oil company's 2011 earnings by 2.5 percent, Bloomberg News reported Friday, citing China International Capital Corp (CICC).

The effect on PetroChina's earnings may reach 5.5 percent if the reform is implemented nationwide, Bin Guan, a CICC analyst, wrote in a report dated yesterday.

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China started levying a five percent tax on oil and gas exploration in 12 western provinces starting Dec 1, Inner Mongolia Daily reported yesterday, citing a joint statement from the country's finance ministry and taxation bureau.

PetroChina declined 1.6 percent to 11.5 yuan ($1.7) as of 11:30 am in Shanghai trading, the report said.