The China National Petroleum Corporation (CNPC), parent company of the nation\'s top oil and gas producer -- PetroChina, predicted on Monday that its natural gas supply at home will increase 13 percent during the upcoming winter and spring seasons. A company spokesman said the CNPC expects its gas supplies during the two seasons will total 57 billion cubic meters. The company forecasted the hike amid robust natural gas demand as some Chinese cities begin using natural gas instead of coal for winter heating in order to reduce damage to the environment. In the Chinese capital Beijing, natural gas supply by CNPC during winter and spring is expected to grow 3 percent to 7.41 billion cubic meters, according to the spokesman. China has been under growing pressure to address the causes of air pollution after heavy smog smothered large swathes of the country early this year. In a government action plan unveiled last month, China vowed to take a multi-pronged approach to tackle air pollution by cutting coal use, shutting down polluters and promoting cleaner production. Under the plan, the country will boost supply of natural gas, coal-based substitute natural gas and coalbed methane.