Last month, Beijing and Washington signed a limited deal to open new markets for each other's exports, and a long-standing friend of the Chinese leadership, Iowa Governor Terry Branstad, was confirmed as U.S. ambassador.
The calls for a response come as spy satellites detected new activity at North Korea's underground nuclear test site for the first time in several weeks, according to two U.S. officials who spoke to CNN.
China's Foreign Ministry said earlier Beijing had made "unremitting efforts" to resolve tensions on the Korean peninsula for its own interests, not due to external pressure.
The prosecutor "told me the United States had moved much quicker to secure the release of female journalists in 2009", Bae said, referring to Euna Lee and Laura Ling, who were released after a short period in North Korean detention following a visit from former USA president Bill Clinton.
"I am committed to improving the US-China defense relationships, so it remains the stabilizing element in our overall relationship", Mattis stated.
Despite sanctions and pressure, North Korea has repeatedly vowed to further develop its missile and nuclear weapons program, viewing it as a deterrent against what it claims is Washington's hostile policy against it.
But on Tuesday, Trump sent a tweet suggesting Xi's efforts had not borne fruit - a message he reiterated before supporters in Iowa.
"What you're seeing, I think, is the American people's frustration with a regime that provokes and provokes and provokes, and basically plays outside the rules". There are few signs that the European Union is internally united on this policy, or that it really has anything to contribute given that it has no military assets in the region and no special relationship with North Korea that offers the prospect of a better negotiation than anybody else has had.
"South Korea must realise that following psychopath Trump.will only lead to disaster", an editorial carried by the paper said.
Pyongyang has long denounced the joint military drills between South Korea and the U.S. as a rehearsal for a northern invasion despite Seoul and Washington's assurance that they are defensive in nature.
"Whatever policy we take has to be in coordination with South Korea", said Dean Cheng, senior research fellow on Chinese military and security issues at the Heritage Foundation, a Washington-based conservative think-tank.
Nauert stressed that the State Department issued a travel warning for North Korea that lays out the dangers.
Mattis said in a press conference after a meeting with Chinese counterparts on Wednesday that he is committed to enhancing the United States partnership with China in the defense sector.
Mattis said China "continues to work these issues".
China provides most of North Korea's food and fuel imports.
It is also a way of signaling Europe's biggest card if it gets truly fed up with the United States: it could always tilt toward China, selling arms and tech to a country many in the USA believe is the greatest long term threat to America's global position.
In one interview, Trump appeared to empathize with Kim, telling Reuters that taking over North Korea after his father's death was "a very hard thing to do".