China has reportedly pledged to buy nearly an extra $US80 billion ($A116 billion) of manufactured goods from the US over the next two years, plus just over $US50 billion in energy supplies under a trade deal set to be signed this week.

Beijing would also boost purchases of US services by about $US35 billion over the same two-year period, a source briefed on the agreement said, aiding a sector that enjoys a rare trade surplus with China.

The Phase 1 agreement calls for Chinese purchases of US agricultural goods to increase by some $US32 billion over two years, or roughly $US16 billion a year, the source said.

When combined with the $US24 billion US agricultural export baseline in 2017, the total gets close to the $US40 billion annual goal touted by US President Donald Trump.