U.S. President Donald Trump will speak with Chinese President Xi Jinping as soon as this week, Trump's spokesperson said, setting up a major diplomatic exchange as the world's two largest economies seek a deal that could avert a broader trade war.

Robert Lighthizer, who was the U.S. trade representative in President Trump's first administration, says China poses an existential threat to the United States that must be urgently addressed by Washington.

President Donald Trump signed an order to put tariffs on U.S. neighbors Canada and Mexico, as well as China, starting Tuesday