Gen. Fan Changlong, a vice chairman of China's Central Military Commission, spoke with Dunford before the meeting with Xi.
"Until somebody solves the part of the equation that shows me that 10 million people in Seoul don't die in the first 30 minutes from conventional weapons, I don't know what you're talking about, there's no military solution here, they got us", he told The American Prospect.
Dunford, who was in South Korea earlier this week and will land in Japan Thursday evening to discuss tensions around North Korea's growing weapons programme, acknowledged that a military solution would be "horrific". Pyongyang has threatened to fire missiles towards the Pacific island of Guam and U.S. President Donald Trump has warned it would face "fire and fury" if it threatened the United States.
Dunford's tour of Asia started in South Korea, where he told President Moon Jae-in that the United States was prepared to use military force against North Korea, but only as a last resort, with economic and diplomatic solutions to be used until exhausted.
"General Dunford delivered a clear message that North Korean ballistic missile and nuclear weapons programs threaten the entire global community, including China, Russia, the U.S. and our allies", said U.S. military spokesman Capt Darryn James in a statement.
U.S. Defense Secretary Jim Mattis, Secretary of State Rex Tillerson and their Japanese counterparts agreed at a meeting in Washington on Thursday to work more closely on North Korea.
"The people worked together to rebuild the country from the Korean War, and we can not lose everything again because of a war", Mr Moon said in a nationally televised news conference.More news: Japan aiming to boost missile defense with US Aegis Ashore system
"Kim Jong Un of North Korea made a very wise and well reasoned decision", Trump wrote on Twitter on Wednesday.
The statement said that during a meeting between Dunford and Song Puxuan, commander of the northern theatre of the People's Liberation Army, Song stressed that efforts to resolve the nuclear issue on the Korean peninsula "should adhere to dialogue and political settlement".
Gen Dunford told reporters that he has advised the USA leadership not to dial back on the exercises with South Korea. Li Jie, a Chinese military analyst, told the South China Morning Post that China was not willing to go beyond economic sanctions.
China's vote was a welcoming sign that Beijing is willing to work with Washington as tensions between the US and North Korea remain tense. "And that's really one of the issues that we will work on".
North Korea's threats against Guam and its advancing missile capabilities, highlighted by a pair of intercontinental ballistic missile flight tests in July, have raised security jitters among many South Koreans who worry that a fully functional ICBM in Pyongyang would force the United States to rethink whether to trade NY or Washington for Seoul in the event of a war on the peninsula.
North Korea has fired missiles and taken other steps in response to the war games in the past.
Moon has repeatedly urged North Korea not to "cross the red line" but had not previously elaborated what that would constitute.