US President Donald Trump China's President Xi Jinping arrive for the state dinner with the first ladies at the Great Hall of the People in Beijing in November 2017. File picture: Thomas Peter/AP

Washington - The United States hit China with 50 billion dollars' worth of new trade tariffs on Friday, triggering an instant reaction from Beijing that it would retaliate in kind.

The US had "provoked a trade war," the Chinese Commerce Ministry said.

"The trade war was started many years ago by them and the United States lost," said US President Donald Trump in an interview with broadcaster Fox just minutes later.

Trump announced in a statement on Friday that the US would impose a 25-per-cent tariff on Chinese products that "contain industrially significant technologies."

The duties, which will make Chinese goods more expensive for US customers, were imposed "in light of China's theft of intellectual property and technology and its other unfair trade practices," the White House statement said.

Trade between the United States and China "has been very unfair, for a very long time. This situation is no longer sustainable," it said.

The new tariffs would take effect from July 6, according to the office of trade representative Robert Lighthizer.

"We must take strong defensive actions to protect America's leadership in technology and innovation against the unprecedented threat posed by China's theft of our intellectual property, the forced transfer of American technology, and its cyber attacks on our computer networks," Lighthizer said.

China had earlier threatened to retaliate if the US imposed import tariffs on its products, and followed through on that threat shortly after the US made its tariffs announcement.

China will "immediately introduce taxation measures of the same scale and the same strength," the Chinese Commerce Ministry said.

"We deeply regret that the United States has disregarded the consensus formed ... and provoked a trade war. This move is not only damaging bilateral interests but also undermining the world trade order."

"In the face of the US' short-sighted behaviour that hurts others and itself, China has to respond strongly and firmly defend the interests of the country and the people, and resolutely safeguards economic globalization and the multilateral trading system," the ministry added.

China called on all countries to take action against the US' "outdated and regressive behaviour."

Releasing details about what products would be affected by the tariffs, the US trade representative's office said "the list of products issued today covers 1,102 separate US tariff lines."

"Goods commonly purchased by American consumers such as cellular telephones or televisions" would not be affected, the office said.

The world's two largest economies have been sparring over trade in recent months, sparking global fears of an all-out trade war.

Trump previously announced tariffs of up to 25 per cent on steel and aluminium from several countries.

In May, after several back-and-forths, Chinese and US officials decided to put tariffs on hold.

But Friday's announcement meant that "all the economic and trade achievements previously reached by the two parties will be invalid," the Chinese Commerce Ministry said.

A further descent into an all-out trade war loomed, with the US vowing to "pursue additional tariffs if China engages in retaliatory measures."