Pentagon chief Jim Mattis on Wednesday warned North Korea to stop pursuing nuclear weapons and stop considering actions that would lead to the "destruction of its people." "The DPRK (Democratic People's Republic of Korea) must choose to stop isolating itself and stand down its pursuit of nuclear weapons.The DPRK should cease any consideration of actions that would lead to the end of its regime and the destruction of its people." General Mattis said. He began by saying North Korea y should bear in mind America's own military and defence capabilities. "The United States and our allies have the demonstrated capabilities and unquestionable commitment to defend ourselves from an attack " President Trump had warned him to ensure America's weapons arsenal was ready. "President Trump was informed of the growing theat last December and on taking office his first orders to me emphasised the readiness of our ballistic missile defence and nuclear deterrent forces. While our state department is making every effort to resolve this global threat through diplomatic means, it must be noted that the combined allied militaries now possess the most precise, rehearsed and robust defensive and offensive capabilities on Earth. <span style='font-family: "Times New Roman", serif; font-size: medium;'>______________</span> "The DPRK regime's actions will continue to be grossly ovematched by ours and would lose any arms race or conflict it initiates." Earlier secretary of state Rex Tillerson tried to ease concerns that the US. was heading toward a military confrontation with North Korea after President Donald Trump rattled global markets with his warning that he could unleash “fire and fury” against Kim Jong Un’s regime. “Americans should sleep well at night, have no concerns about this particular rhetoric of the last few days,” Mr Tillerson said during his flight back to the US following a tour of south-east Asia. The president “felt it necessary to issue a very strong statement directed at North Korea,” he said. But the statement fromMr Matttis, a retired general,was entirely in keeping with Mr Trump's more belligerent tone. His warning to North Korea to "cease any consideration of actions that would lead to the end of its regime and the destruction of its people" echoed the president's "fire and fury" threat. Mr Trump’s threat reverberated around the world, sparking a market sell-off and prompting a wave of criticism even from members of his own political party. Senator John McCain of Arizona, the Republican chairman of the Senate armed services committee, said he wasn’t sure Trump was ready to act, while Senator Ben Cardin of Maryland, the top Democrat on the Senate foreignrRelations committee, said Mr Trump’s language was counterproductive. The president returned to Twitter on Wednesday morning with a posting about the US nuclear arsenal which, he said, “is now far stronger and more powerful than ever before.” In a follow-up message he added, “Hopefully we will never have to use this power, but there will never be a time that we are not the most powerful nation in the world!” “It’s not the way you should be conducting foreign policy,” was Senator Cardin's reaction on MSNBC’s “Morning Joe’’ television programme. “What the president is doing by making his own unilateral decisions that indicate that we’re ready to start a military confrontation -– that’s just moving in the wrong direction.’’ Markets retreated for a second day amid the heightened tensions. The S&P 500 Index lost 0.1 percent to 2,472.58 at 12:26 p.m. in New York, after declining 0.2 percent on Tuesday, the largest decrease in almost five weeks. The Stoxx Europe 600 Index declined 0.7 percent, and the CBOE Volatility Index rose 3.8 percent to 11.40. Mr Tillerson said the US. is engaged in a very active diplomatic effort to halt Mr Kim’s pursuit of a nuclear weapon that could strike America's mainland. He said North Korea should be looking for talks “with the right expectation of what those talks will be about.” Mr Trump’s threat to hit North Korea came as that nation -- reacting to new United Nations sanctions against its nuclear program -- warned the US would “pay dearly” and said it was examining plans to fire a missile toward an American military base on the Pacific island of Guam - a major US military base. The exchange followed a Washington Post report, citing an analysis by the Defence Intelligence Agency which concluded Pyongyang has successfully developed a nuclear warhead that will fit on its missiles. While global powers and financial markets have long been accustomed to over-the-top rhetoric from North Korea, the US has traditionally taken a more diplomatic stance. Mr Trump’s suggestion that he might meet Kim’s threats with action startled markets and prompted a renewed focus on the narrowing list of options available. Mr Trump and his chief of staff, retired General John Kelly, were in constant contact with the White House national security team regarding North Korea before the president made his comments, said White House spokeswoman Lindsay Walters in Bedminster, New Jersey, where Mr Trump is on holiday. But she and other administration aides declined to say whether the specific language used by the president were part of those consultations or whether Mr Tillerson and Mr Mattis took part in the discussion. Mr Trump’s threats may be straining the credibility of his office. Officials in South Korea - one of the nations most at risk in any potential armed confrontation between its northern neighbour and the US - officials largely brushed off Mr Trump’s warning., saying there was no “imminent crisis.” A senior Japanese official said very few people in the government were taking Mr Trump’s comments seriously. Seoul Vulnerable But Trump’s comments and Kim’s threat to strike the U.S. mainland revived concerns in the region about the protection of the American nuclear umbrella. In the event of a military confrontation, it’s not likely that the U.S. would be able to immediately knock out all of North Korea’s capability, leaving the 10 million people in Seoul vulnerable to an artillery and rocket barrage. “The prioritization of the American homeland and the security of the American homeland is upsetting a lot of understood truths: The idea that the U.S. would defend Seoul as if it were Los Angeles,” said John Park, director of the Korea Working Group at Harvard Kennedy School. “Now the view is, in order to protect the American homeland, collateral damage over there is acceptable.” Senator Lindsey Graham said Wednesday that Trump’s rhetoric created a “red line’’ that made it clear that the U.S. would be willing to take action if North Korea didn’t pull back. “This is not a language problem. This is a North Korean regime trying to get the capability to strike America,’’ the South Carolina Republican said on “CBS This Morning.’’ “We’ve failed for 30 years. It’s time to try something new.” In a statement on Wednesday, China urged all sides to avoid escalating tensions and to return to dialogue, a statement echoed by diplomats at the United Nations. UN Reaction “This kind of rhetoric doesn’t help at all,” Sacha Sergio Llorenty Soliz, Bolivia’s ambassador to the UN, told reporters in New York. “What has been said by President Trump and Kim Jung Un is really detrimental to purposes of the UN charter.” Countries should focus on implementing the latest round of UN sanctions, which targeted about $1 billion in North Korean exports, Carl Skau, Sweden’s deputy UN ambassador, said. “The resolution is not only about sanctions and putting pressure on the North Koreans,” Skau said. “It’s also about the importance of dialogue and the humanitarian aspect as well.” North Korea’s reported progress on miniaturizing nuclear warheads -- coupled with two test flights of intercontinental ballistic missiles in July -- are raising pressure on Trump. Before taking office, he pledged to prevent North Korea from developing an ICBM: “It won’t happen,” he wrote on Twitter. While Kim’s efforts to develop a missile capable of delivering a nuclear weapon to the continental U.S. face big technological hurdles, he has made significant progress. He still needs a rocket that can survive reentry and a guidance-and-control system capable of directing it to the U.S. without breaking up.