"China has always believed that protectionism offers no way out and that there are no winners in trade wars and tariff wars," foreign ministry spokeswoman Mao Ning said, when asked about the tariffs at a daily news conference.

"The United States' actions seriously violate (World Trade Organization) rules, seriously damage the rules-based multilateral trading system and are not conducive to solving the problem," said Mao.

"China will also take all necessary measures to safeguard its legitimate rights and interests," she added.

US President Donald Trump's 25 percent duties on steel and aluminium imports took effect at 0401 GMT Wednesday and mark a new stage in the trade war between the United States and its main trading partners.

China is the world's leading steel manufacturer, though not a major exporter of the product to the United States.

Earlier this month, Trump raised a blanket tariff of 10 percent he previously imposed on all Chinese products to 20 percent, provoking retaliatory levies by Beijing on certain US agricultural goods.