Prominent American investor Jim Rogers has warned in a new book that the worst economic downturn in his lifetime is around the corner and that Japan's future is in jeopardy unless it takes serious steps to deal with staggering debt and a declining birth rate.

In an interview with The Japan Times in Tokyo on Tuesday, the chairman of Rogers Holdings Co. Inc. said that even though the United States and China are poised to reach a trade agreement, any euphoric mood will be temporary. He predicted that U.S. President Donald Trump will ramp up trade wars in earnest to boost his re-election bid in 2020 as the economy slows down.

"Later this year or next, when things are getting bad in the world economy — therefore America is going to start suffering — and Mr. Trump has an election in 2020, he is going to say 'we got to bash these guys,'" Rogers said. "That's when Japan, China and other people are going to feel more effects of trade war because he thinks it will help him win the election."