China National Petroleum Corp. (CNPC.YY) plans to raise CNY20 billion ($3.18 billion) of bills in April, a person familiar with the situation said Thursday.

The bills are likely to have a maturity of six or nine months, but the company has yet to decide on the details, said the person, who declined to be named.

China's largest oil company by assets will use the proceeds to supplement its working capital, the person said.

CNPC is rated triple-A by China Lianhe Credit Rating Co.