A corn purchaser writes on his account in northwest China in 2012. In November 2013, officials began rejecting imports of U.S. corn when they detected traces of a new gene not yet approved in China. Peng Zhaozhi/Xinhua/Landov hide caption

itoggle caption Peng Zhaozhi/Xinhua/Landov

A worker stacks traffic safety poles at Pexco's manufacturing center in Fife, Wash. The small company ships products all over the world, with the help of federal insurance from the Export-Import Bank. Drew Perine/MCT/Landov hide caption

itoggle caption Drew Perine/MCT/Landov

Shipping containers sit at a port in Tianjin, China, on Feb. 28. Alexander F. Yuan/AP hide caption

itoggle caption Alexander F. Yuan/AP