He added, "We call on all countries to redouble their efforts, including through implementation of agreed UN Security Council resolutions, to bring North Korea to its senses and end its reckless and unsafe threats to the peace of our region and the world".
"North Korea is very good at smokescreen".
The statement was in response to the 10-day exercise, codenamed Ulchi-Freedom Guardian, involving US and South Korean troops that began on Monday.
Analysts have said all eyes will be on the war game that could send tensions spiralling back upwards after the war of words between the United States and North Korea appeared to have cooled off slightly. -South Korean military drills with its standard fiery threats, vowing "merciless retaliation" for exercises Pyongyang claims are an invasion rehearsal.
"This is aimed to ignite a nuclear war on the Korean peninsula at any cost", the North's KCNA news agency said. In a commentary carried by the official Rodong Sinmun newspaper, the North warned of an "uncontrollable phase of a nuclear war" on the peninsula.More news: North Korea warns of nuclear war over USA military drills with South
It involves tens of thousands of South Korean soldiers.
North Korea's rapid progress in developing nuclear weapons and missiles capable of reaching the U.S. mainland has fueled a surge in tension.
China, North Korea's main ally and trading partner, has urged the United States and South Korea to scrap the exercises.
He said diplomacy was "the most important starting point" in response to the North's threat, when asked what actions by North Korea might trigger a preemptive USA strike against Pyongyang.
Seoul and Washington have said the largely computer-simulated UFG exercise, which dates back to 1976, will go ahead as planned, but did not comment on whether the drills would be scaled back in an effort to ease tensions.More news: Trump's Shortsighted Tirades at Republicans Could Hurt Him
A confidential United Nations report, seen by Reuters on Monday, found North Korea evaded U.N. sanctions by "deliberately using indirect channels" to export banned commodities and had generated $270 million between October 2016 and May 2017.
The Security Council unanimously imposed new sanctions on North Korea on August 5 that could slash its $3 billion annual export revenue by a third. Ties between the Koreas are nearly always fraught, but anxiety is higher than normal following weeks of tit-for-tat threats between President Donald Trump and Pyongyang in the wake of the North's two intercontinental ballistic missile tests last month.
But the sharp rhetoric of last week has since softened, with North Korea leader Kim Jong-un putting the Guam plans on hold - a move praised by President Trump.
"In the event of a missile launch towards the territory of Japan, Guam, United States, Korea, we would take immediate, specific actions to take it down", Mattis said. Bay State U.S. Sen.
While the allies are pushing ahead with the exercises that date back to 1976, around 17,500 USA troops will participate in the drills - a cutback from a year ago.More news: Bloodiest week in the Philippines' War on Drugs
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