Speaking at the International Institute for Strategic Studies' annual Asia security conference the morning of June 3 in Singapore, which was the evening of June 2 Washington time, Mattis told the annual gathering of the region's defense elite that North Korea poses "a clear and present danger" to the United States.
Mattis also wanted to reaffirm the USA commitment to strengthen alliances in the region, an issue that has been in question after Trump assumed office and made decisions, including Washington's withdrawal from the Trans-Pacific Partnership.
The pair of Japanese Naval Vessels and US Aircraft carriers have introduced a joint drill in the Sea of North Korea on Thursday.
North Korea's aggression "cannot continue", Mattis said during a summit in Asia..
China's territorial claims in the resource-rich South China Sea are contested by several nations.President Donald Trump and other senior U.S. officials have repeatedly stated that America would protect its interests in the South China Sea, a key shipping route.
These partners include China, with Mattis saying that the Trump administration is encouraged by its " renewed commitment to work with the global community toward de-nuclearization, " adding that he believed China will eventually see North Korea as a strategic liability and not an asset given its propensity for inciting disharmony.
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Calling North Korea's nuclear ambitions a "threat to us all", Mattis said the worldwide community must work together. North Korea is one area where the United States and the rest of the world need Chinese help to rein in North Korea's Kim Jong Un.
Sky News understands the United States has not yet asked Australia to join freedom of navigation exercises in the South China Sea - despite both countries issuing stern warnings for China to respect its neighbours.
The mounting tensions with its neighbor led South Korea to ask the USA for installation of the Terminal High Altitude Area Defense missile system on the peninsula.
Australian Prime Minister Malcolm Turnbull also urged China to act responsively on issues such as the Korean Peninsula in a speech on Friday evening.
The United Nations is levying more sanctions on North Korea.
"Words must be followed by actions", Mattis said.
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He plays nearly as a sweeper and can see in advance what is going to happen. "We're not favourites, nor are Juventus". We're not going to change anything that we did and we're going to give it our all.
Mattis' remarks triggered a question about whether there is any change to the U.S.'s "one China" policy, which was asked by a participant from China who felt it was unusual that the USA expressed its intention to strengthen defense links with Taiwan on such an occasion.
One questioner asked if the USA president was an "unbeliever" in the rules-based regional order.
The 15-member council voted unanimously to back the sanctions after weeks of negotiations between the United States and China.
The defense secretary added: "We oppose countries militarizing artificial islands and enforcing excessive maritime claims unsupported by worldwide law. We will work closely with China where we share common cause".
"If the U.S. and its President continue to see allies and partners as purely transactional. that's going to put stress on relationships", said Ben Shreer, a defense analyst with the International Institute of Strategic Studies, the think-tank that organizes the defense conference.
"This step is something that is very puzzling and deeply disappointing", Deputy Russian UN Ambassador Vladimir Safronkov said of the US sanctions amid battered US-Russia relations.
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In January, Trump signed an executive order blocking the entry of people from Iraq, Somalia, Iran, Syria, Sudan, Libya and Yemen. The justices usually go on a summer recess at the end of June after having issued their opinions in all the pending cases.