North Korea's growing nuclear capabilities amount to a "direct threat to our security and the security of the entire world", Tillerson told the 15-nation council at a high-level meeting on nuclear nonproliferation convened by Japan, which now holds the UNSC rotating presidency.
North Korea faces the danger of a nuclear catastrophe - not war with the U.S. - but the possibility of a China Syndrome-type accident at one of its domestic nuclear reactors.
Washington will use all necessary means to defend itself against North Korean aggression, he said, but it also hopes to resolve the issue through diplomacy.
Tillerson said Friday that diplomatic discussions must be preceded by a "sustained cessation" of the North's threatening behavior. And after suggesting earlier this week that the Trump administration would be open to talks with North Korea after a period of calm and without the USA imposing other "preconditions", Tillerson pulled back from that formulation. "The pressure campaign must and will continue until denuclearization is achieved", Tillerson told the meeting.
Tillerson added: "We will in the meantime keep our channels of communication open".
He said the USA will not accept, as a precondition of talks, ending existing sanctions.
Throughout the year, the regime has also conducted 20 ballistic missile launches, including the first tests of two intercontinental ballistic missiles (ICBMs), as well as new medium- and intermediate-range ballistic missiles.
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To the other members of the global community, the secretary urged full implementation of U.N. Security Council sanctions against Pyongyang and additional independent steps to deprive the regime of funding for its weapons programs.
Tillerson was addressing the U.N. Security Council Friday.
In his Friday speech, Tillerson returned to a tougher stance and took particular aim at what the administration sees as lackluster effort by China and Russian Federation to pressure Pyongyang.
Tillerson's United Nations appearance is the latest push in the Trump administration's effort to persuade other countries to isolate North Korea by kicking out its diplomats and cutting remaining economic links.
Tillerson said that continuing to allow North Korean laborers to toil in "slave-like conditions" for wages used to fund nuclear weapons "calls into question Russia's dedication as a partner for peace".
Wu also urged Washington to tone down its belligerent rhetoric, saying "there is no military option when it comes to the settlement of the nuclear issue of the Korean Peninsula", he said. It said North Korea's actions "are not good for anyone and certainly not good for North Korea". On Sept. 3, Pyongyang conducted its sixth nuclear test the year, unleashing an natural disaster of 6.1 magnitude. In a rare appearance at the council, North Korea's United Nations ambassador was present at the meeting and expected to speak after council members.
"The DPRK remains the only country to continue to break the norm against nuclear testing", Guterres noted, using the abbreviation for North Korea's formal name. They should agree to what we propose: "'Put your drills - which, in principle, are a provocation by the USA against the North - on hold for the talks to start", Kim said.