Chinese maritime officials said China National Offshore Oil Corp.'s rig should be near the Gulf of Tonkin. It left port earlier this week as Chinese and Vietnamese officials tried to find a resolution to disputes that began when a rig was deployed in contested waters in May.
Yun Sun, a Chinese security analyst at Washington think tank Stimson Center, told Vietnam's Thanh Nien News the timing of the second rig's deployment was deliberate.
"The decision certainly suggests China's unwillingness to abandon its coercive approach," he said in an interview published Friday.
It was unclear if the second rig would be deployed in disputed waters.
Both sides say the rig sent in early May is positioned in territories they control.
Australian Foreign Minister Julie Bishop told Voice of America her government was calling on all sides to find a way to reduce the tensions.
"Australia does not take sides in specific disputes, but we call on parties to negotiate and to resolve the issues in accordance with international law," she said.