India's government is in favour of banning imports of petroleum coke to curb air pollution, according to a government affidavit filed with its top court, which could be a big blow to US refiners who export heavily to the country.

The Supreme Court, which in October banned the use of petroleum coke in and around New Delhi in a bid to clean the air in one of the world's most polluted cities, on Monday deferred a scheduled hearing on a case on its use across the country to Wednesday.

India is the world's biggest consumer of petroleum coke, better known as petcoke, which is a dark solid carbon material that emits 11 percent more greenhouse gases than coal, according to the Carnegie–Tsinghua Centre for Global Policy.

Burning it also emits several times more sulphur dioxide, which causes lung diseases and acid rain. Local producers include Indian Oil Corp, Reliance Industries and Bharat Petroleum Corp.

The oil ministry has also told the Supreme Court that petcoke should only be used as feedstock, like in the cement industry, and not as fuel.