Newly-elected South Korean President Moon Jae-in and his Chinese counterpart Xi Jinping held their first phone call on Thursday afternoon, according to the Blue House, agreeing to work together to pressure North Korea to freeze its nuclear and missile programs.
The Trump administration has also been dismayed by Moon's questioning of deployment of a United States missile defence system in South Korea and expects some friction in ties, although USA officials say the new president may moderate his stances in office and the effect on the alliance will be limited.
There's widespread opposition in South Korea to the THAAD deployment and loud protests from China, which also sees the system as a security threat.
Xi told Moon that China has always upheld the denuclearisation of the Korean peninsula and that the nuclear issue should be resolved through talks, which are in everyone's interests, according to the state television report.
"We are well aware of China's concerns and concerns about the deployment of the THAAD", Moon said.
Trump congratulated Moon on his election victory and promised to invite him to Washington.
Most successful tests have landed missiles into the Sea of Japan, but spectators have agreed that the tests are steps to extend North Korea's reach of nuclear weapons to other areas of the world.
The South's 19th president - the son of refugees from North Korea - had during his campaign advocated for a combination of negotiations and economic cooperation alongside military and security measures in dealing with the North. President Trump has vowed to fix or scrap the trade deal.
In January, Tokyo withdrew two diplomats from South Korea after a statue of a "comfort woman" was erected outside the Japanese consulate in the southern city of Busan, arguing it breached the 2015 agreement. Xi said China was willing to handle disputes with South Korea "appropriately" on the basis of mutual trust and understanding.
Moreover, although Trump has used some tough rhetoric when it comes to North Korea and its leader, the US government has wavered multiple times on the matter.
The deployment of THAAD was agreed by former President Park Geun-hye's administration a year ago. But a WSJ op-ed by Michael Breen said Moon's approach is likely to be more realistic than the "sunshine policy".
While taking the oath of office Wednesday, Moon said he's open to visiting North Korea under the right conditions.
The concern of South Korea becoming a puppet to Washington was undoubtedly an asset to Moon.
Mr Moon has adopted a more conciliatory tone towards the North - backing diplomatic engagement and suggesting he could visit Pyongyang for talks. That played into the hands of Moon, who has written that South Korea should "learn to say no" to Washington.
If they had, North Korea might have become more dependent on South Korea than on China, in which case US and South Korean leaders would not have to plead constantly with China to rein in the North Korean regime.
South Korea has accepted a last-minute invitation from China to a conference on a new Silk Road, days after a new president took office on Seoul pledging to engage in discussions with Beijing to ease tension over a USA anti-missile system.