Could this be related with North Korea’s warning of war I posted here yesterday?
Remember, China and North Korea are allies.

Pentagon: Chinese vessels harassed unarmed ship

WASHINGTON (AP) – The Pentagon charged Monday that five Chinese ships shadowed and maneuvered dangerously close to a U.S. Navy vessel in an apparent attempt to harass the American crew.Defense officials in the Obama administration said the incident Sunday followed several days of “increasingly aggressive” acts by Chinese ships in the region. The incident took place in international waters in the South China Sea, about 75 miles south of Hainan Island.

Several days, I don’t believe this is a coincidence. I believe this is China’s way of telling us to leave North Korea alone.