US President Donald J. Trump reacts at the Florida State Fairgrounds Expo Hall in Tampa, Florida, USA, 31 July 2018. Trump continues to hold rallies around the country in support of his agenda and candidates running in the mid-term elections. EPA-EFE/ROD MILLINGTON 
The US imposed 25 percent tariffs on $34 billion of Chinese products earlier this month, with plans to add another $16 billion of imports on Tuesday.
Trump initially threatened to levy 10 percent on an additional $200 billion but that figure may now rise to 25 percent, sources told the Washington Post and Bloomberg.
It would represent a ramping up of pressure over Washington's trade standoff with Beijing.
Markets were however steady on Tuesday, given a boost by hopes for new negotiations.
In 2017, the United States had a $376 billion trade deficit with China, which it is keen to cut.
Trump recently threatened to slap punitive tariffs on all Chinese imports, which accounted for more than $500 billion last year. DM