U.S. President Donald Trump often tweets from his iPhone about pressuring China to address its $375 billion trade surplus with the United States. But a closer look at the Apple smartphone reveals how the headline figure is distorted.

The big trade imbalance — at the heart of a potential trade war, with Trump expected to impose tariffs on Chinese imports this week — exists in large part because of electrical goods and tech, the biggest U.S. import item from China.

Apple Inc.'s iPhone, however, illustrates how a big portion of that imbalance is due to imports of American-branded products — many of which use global suppliers for parts but are put together in China and shipped around the world.