The North Korean government last week said it was considering a third nuclear test.
Chinese Foreign Ministry spokesman Hong Lei said Monday that Beijing rejects any action that may lead to an escalation of tensions in the region.
"We hope that all relevant parties will remain calm and restrained, as well as work to maintain peace and stability in northeast Asia," he was quoted by the official Xinhua news agency as saying.
Blog 38 North from the U.S.-Korea Institute at Johns Hopkins University states that satellite imagery of the Punggye-ri Nuclear Test Facility from last Wednesday reveals that the site "appears to be at a continued state of readiness that would allow the North to move forward with a test in a few weeks or less once the leadership in Pyongyang gives the order."
In December, North Korea, after a failed attempt in April, launched a long-range rocket to put a satellite into orbit. Launches in 2006 and 2009 coincided with the testing of nuclear devices.
China is party to stalled multilateral nuclear negotiations with North Korea.