UPDATE Feb. 4 9:37am: Chinese Foreign Ministry spokesman Lu Kang on Saturday reasserted China's claim of sovereignty over the East China Sea islands following remarks by President Donald Trump's defense secretary that a U.S. commitment to defend Japanese territory applies to an island group that China claims, according to the Associated Press.
China responds to Mattis
"We urge the U.S. side to take a responsible attitude, stop making wrong remarks on the issue involving the Diaoyu islands' sovereignty, and avoid making the issue more complicated and bringing instability to the regional situation," Lu said.
US Defence Secretary James Mattis said any use of nuclear weapons by North Korea will result in an "effective and overwhelming" response.
Mattis visited South Korea where he reassured leaders that the alliance between the countries will remain strong and reconfirmed plans to deploy a US missile defense system in South Korea later this year, BBC reported.
"Any attack on the United States, or our allies, will be defeated, and any use of nuclear weapons would be met with a response that would be effective and overwhelming," Mattis told reporters
The U.S. has a strong military presence along the South Korean border of North Korea as the U.S. has promised protection for South Korea since the two Koreas remain at war, even after the 1953 armistice agreement that supposedly ended the Korean war.
North Korea has conducted two nuclear tests in 2016 and over 20 missile tests in 2016 defying UN resolutions and sanctions. There is concern that they are gearing up to test a new ballistic missile.
North Korean leader Kim Jong Un said in a New Year's address that they are close to testing the missile.
President Trump, however, has said that won't happen.
North Korea just stated that it is in the final stages of developing a nuclear weapon capable of reaching parts of the U.S. It won't happen!— Donald J. Trump (@realDonaldTrump) January 2, 2017
China isn't thrilled about US missile defense system
The deployment of the missile defense system or Thaad, terminal high-altitude area defense, in South Korea has China on edge.
China believes that Thaad will destabilize the regional security balance and South Korean opposition have called for the program to be delayed of cancelled, according to the Guardian.
The Associated Press contributed to this report.