The Ministry of Ecology and Environment unveiled on Wednesday a work plan to include three industrial sectors into the country's carbon trading program, signifying the initiation of the program's inaugural expansion phase.

Launched in 2021, China's carbon trading market, already world's largest, currently involves 2,200 coal-fired power generation companies, which annually contribute about 5 billion metric tons of carbon dioxide.

The work plan aims to extend the trading program to about 1,500 companies in three other major carbon emitters — steel, cement, and aluminum smelting, according to a media release from the ministry.

The three industries collectively emit about 3 billion tons of carbon dioxide equivalent a year, representing 20 percent of China's total carbon dioxide emissions, it said.

The expansion means that 60 percent of the carbon dioxide emissions in China will be covered by the national program, it noted.