President Donald Trump said the US has cancelled plans to impose new tariffs on $US160 billion ($233 billion) worth of Chinese imports as part of a modest interim agreement that de-escalates a 17-month trade war.

The US is also reducing existing import taxes on about $US112 billion ($163 billion) in Chinese goods from 15 per cent to 7.5 per cent.

In return, Mr Trump said on Twitter that the Chinese have agreed to “massive” purchases of American farm and manufactured products. He did not specify how big those purchases would be.

Chinese officials said if Washington reduces the tariffs, Beijing will lower its trade penalties on American goods and also scrap plans for new tariffs from Sunday.

“China is ready to work with the US side to do more to promote growth in trade,” China’s deputy finance minister Liao Min said on Friday.

Asked to confirm reports that Beijing had committed to buy $US50 billion ($73 billion) of American farm goods, he said details would be released later.

The “phase one” deal leaves unresolved some of the thorniest issues, but Mr Trump said work on a follow-up would begin “immediately, rather than waiting until after the 2020 Election. This is an amazing deal for all. Thank you!”

Before Friday’s announcement, Chinese foreign minister Wang Yi had complained during a government-organised forum in Beijing that Washington was unfairly attacking China.

“The US side has successively imposed unjustified restrictions and crackdowns on China in economy and trade, science and technology and personnel exchanges,” he said.

“As far as China is concerned, what we are pursuing is our justified rights of development.”

Since July 2018, the Trump administration has imposed import taxes on $US360 billion ($524 billion) in Chinese products.

Beijing has retaliated by taxing $US120 billion ($175 billion) in US exports, including soybeans and other farm products that are vital to many of Mr Trump’s supporters in rural America.

On Sunday, the US was set to start taxing an additional $US160 billion ($233 billion) in Chinese imports, a move that would extend the sanctions to just about everything China ships to America.