Long-threatened tariffs from U.S. President Donald Trump have plunged the country into a trade war abroad — all while on-again, off-again new levies continue to escalate uncertainty.

Trump, who imposed a wave of tariffs on China in his first term, has slapped another 20% duty on a wide swath of Chinese goods this year. Beijing, the top buyer of American agricultural products, recently imposed retaliatory tariffs of 10% to 15% on a range of U.S. exports like chicken, corn, soybeans and beef.

A trade policy expert explains why Trump and Xi should refrain from a trade war and how they can strike a bigger deal.