China Postal Express & Logistics Co is seeking 9.98 billion yuan ($1.6 billion) in an initial public offering as it struggles to keep pace with a domestic delivery market growing 20 percent a year, Bloomberg reported Wednesday.

The country's biggest courier, which retains about 30 percent of the market, intends to buy trucks, airplanes and distribution centers following the IPO.

The Beijing-based company also plans to place a greater focus on the online-shopping market that will grow to 18 trillion yuan by 2015, up from the 4.5 trillion yuan in 2011, according to a five-year plan by the Ministry of Industry and Information Technology.

Nationwide express-delivery sales may increase 20 percent annually, reaching 143 billion yuan in 2015, China Postal said in the share-sale document, citing a government plan.

The prospectus said the sale will take place this year. The sale, arranged by Citic Securities Co, will be Shanghai's largest IPO since builder Sinohydro Group Ltd raised 13.5 billion yuan last year.

China Postal has built up a chain of 45,418 outlets, predominately in post offices run by parent China Post Group. It also has 889,000 employees, according to data compiled by Bloomberg.