China in early May sent an oil rig to waters in the South China Sea contested by Vietnam. The Chinese government sent a letter this week to U.N. Secretary-General Ban Ki-moon to make its case that the operations were within its sovereign right.
Vietnam countered by saying the oil rig's deployment was exacerbating ongoing disputes over claims to the maritime territory.
In a letter planned for the U.N. General Assembly, Hanoi called on China to move the rig, "escort vessels from Vietnam's maritime zones and stop all activities that are interfering with maritime safety and security, and affecting regional peace and security."
China says drilling operations in the region have been ongoing for the last 10 years. The current program, which began May 2, should continue through the middle of August.