'Will defend interests': China puts US on notice after new sanctions on Iran

China has warned that it could take retaliatory measures if the United States significantly expands secondary sanctions targeting Chinese companies doing business with Iran, according to reporting by the Financial Times.The warning came after the Trump administration on Monday announced new sanctions targeting companies in Hong Kong and mainland China as part of a broader crackdown on Iran's oil trade. The measures, however, did not target major Chinese financial institutions, FT reported.A Chinese foreign ministry spokesperson said on Tuesday that Beijing would take "all necessary measures" to safeguard its rights and interests, while reiterating China's opposition to what it described as unilateral sanctions lacking a basis in international law or United Nations Security Council authorisation.The spokesperson also called for de-escalation and a return to dialogue and negotiations.China is Iran's largest oil customer, with Chinese buyers accounting for about 90% of Iran's oil exports.