"But to maintain its role in the North Korea issue, it may try to use its influence over Pyongyang without overstepping, in making the North return to the negotiation table with Washington", he added.
North Korea has chose to deport a U.S. citizen detained for illegally entering the country, its state media reported on Friday. Sweden handles consular issues for US citizens in North Korea.
According to NPR, "North Korea's official KCNA news agency identified the American as Bruce Byron Lowrance and said that he had told his captors that he was controlled by the CIA".
The KCNA did not say exactly when the man would be released. He died not long after, on June 19, 2017.
As worldwide sanctions on North Korea remain intact, China is Pyongyang's sole major ally and a key economic lifeline for the isolated country.
He was detained in January 2016 in Pyongyang on his way home from North Korea. Warmbier and other previous American detainees in the North were imprisoned over a variety of alleged crimes, including subversion, anti-state activities and spying.
Secretary of State Mike Pompeo on Friday expressed appreciation for the co-operation of North Korea and the embassy of Sweden - which handles consular issues for USA citizens in North Korea - "in facilitating the release of an American citizen".
U.S. Vice President Mike Pence, attending a Southeast Asian summit in Singapore, cited the "great progress" made on North Korea but said more had to be done.
Julian Assange charged in US
Throughout that time , the United States has refused to say whether there are any sealed charges against Assange. The Washington Post reported that charges have been drawn up for Mr Assange but it is not clear on what grounds.
Often it takes a high-profile American official to travel to the country and ask for the captive's release.
The weapon does not appear to be a nuclear device or a long-range missile that could target the mainland USA; however, any mention of weapons testing could impact now stalled diplomatic talks between Washington and Pyongyang that aim to rid the North of its nuclear arsenal. South Korean claimed this was "nothing new", and President Donald Trump claimed to have already known about the bases.
Mattis was particularly criticized comments made at a joint news conference last month, when he said the USA military's goal was to ensure the country's diplomats speak to the North from a "position of strength".
"This is sort of like the North Korean version of military reform", said Choi Kang, vice president of the Asan Institute for Policy Studies in Seoul.
The North Korean soldier who defected to the South in a hail of bullets a year ago is a general's son but says most Northerners of his age have no loyalty to Kim Jong Un, according to a Japanese newspaper.
The climate changed dramatically early in January when Kim Jong-un began his "charm offensive", based on North Korea's participation in the Olympics games in Seoul, South Korea. If true, the findings are not surprising; the North has not yet agreed to halt development of nuclear weapons or missiles, although it has staged no tests since the summit. Trump said in September that sanctions will remain in effect against North Korea until denuclearization takes place.
Trump and Kim are both interested in another summit, but it's unclear when it might happen.