US President Barack Obama in March delivered a stark admonition to Xi Jinping over the South China Sea, warning the Chinese leader of serious consequences if China reclaimed land at Scarborough Shoal, one of the most dangerous flashpoints in Asia.
According to current and former officials, Mr Obama raised the stakes with Mr Xi after US intelligence concluded that China was moving towards reclaiming land at the shoal where Chinese and Philippines ships engaged in a high-stakes confrontation in 2012.
Following the meeting in Washington, China withdrew its ships from the area. That gave the White House a victory that some officials saw as vindication for a tougher approach than over the previous three years when it failed to force China to curb its controversial activities in the South China Sea.