Warren Buffett has ignored calls to divest his holding in China's largest listed company, PetroChina, despite calls for him to sell the stake because the company's parent does business in Sudan, accused by the US Congress of genocide.

Buffett, though his Berkshire Hathaway investment company, is the largest foreign shareholder in PetroChina. He has come under fierce criticism from investors for investing in the company, whose parent is China National Petroleum Corporation.