"He told me off the record he may go (to) US$30 billion — US$30 billion, think of this," Trump said Tuesday during a press conference at the White House.
"But he told me that off the record, so I promised I wouldn't tell anybody."
When announced last week, Trump said the plant would initially create 3,000 jobs and could lead to up to 13,000.
The main product being manufactured at the factory will be high-resolution liquid-crystal displays.