Geng said both bilateral and global issues would be taken up during the dialogue, which will be led on the USA side by Secretary of State Rex Tillerson and Defense Secretary Jim Mattis.
Geng said China remains committed to banishing nuclear weapons from the Korean Peninsula and working with the US and others on restarting talks over the issue.
"The military dimension today is in support of the diplomatic and economic effort led by the State Department and at the same time we have an effective posture in the region to deter KJU (Kim) and also to respond in the event that deterrence fails".
"We reaffirmed our commitment to implement in full all relevant U.N. Security Council resolutions".
The meeting of top USA and Chinese diplomats and defense chiefs was held a day after President Donald Trump said China's efforts to use its leverage with Pyongyang had failed, raising fresh doubts about his administration's strategy for countering the threat from North Korea. "For example, we both agreed that our companies should not do business with any United Nations -designated North Korean entities in accordance with these resolutions", he said.
Trump tweeted on the eve of the security dialogue that, "While I greatly appreciate the efforts of President Xi and China to help with North Korea, it has not worked out. At least I know China tried".
Trade and investment are also due to take a high profile following President Donald Trump's repeated complaints about the US trade deficit with China, which hit $310 billion previous year, by far the largest imbalance with any country.
As a first step, Pyongyang may suspend its nuclear and missile activities in exchange for the suspension of large-scale Washington-Seoul military exercises.
"While the USA might not yet have come to terms with China's rise, and despite the fact that China and the United States have not had much cooperation on security issues in the past, it has now become so acute that they must find ways to manage their divergent strategic, security and economic interests", he said.
He said the Pentagon would maintain lines of communication with the Chinese military to head off any escalation in the South China Sea - but keep this separate from the diplomatic effort on North Korea.
The talks followed what a US official said on Tuesday were new movements detected by USA spy satellites at North Korea's nuclear test site.
The discussion, to be held Wednesday at the State Department and hosted by Mattis and Secretary of State Rex Tillerson, is significant, said David F. Helvey, performing the duties of assistant secretary of defense for Asian and Pacific security affairs.
Mattis said Warmbier's death goes "beyond any understanding".
He says the student, Otto Warmbier, had gone there a healthy man and ended up dead after "a minor act of mischief".
Mattis says China shares the USA desire for denuclearization of the Korean Peninsula, and "continues to work this issue".