Tension on the Korean Peninsula has risen this month, with the Trump administration stepping up pressure on North Korea and two major anniversary events in North Korea.
"They don't produce enough food to feed themselves".
US Vice-President Mike Pence, who has been visiting the region, warned the North not to test Washington and said the US "era of strategic patience" with Pyongyang was over.
"In the case of our super-mighty preemptive strike being launched, it will completely and immediately wipe out not only US imperialists' invasion forces in South Korea and its surrounding areas but the USA mainland and reduce them to ashes", it said.More news: Ichiro hits home run in potential final at-bat in Seattle
Earlier in the day, the North Korean state media, the Rodong Sinmun, issued an aggressive warning to the U.S.
U.S. Secretary of State Rex Tillerson plans to preside over a Security Council meeting next week on North Korea. Developing a hydrogen bomb is also a declared priority of North Korea, officially the Democratic People's Republic of Korea or DPRK. "The problem will be taken care of", President Trump insisted. It responded to America's latest threats by firing a missile on Sunday, which exploded seconds later.
Pyongyang said it may test missiles on a weekly basis, and warned of "all-out war" if the U.S. takes military action.
Mr Mattis credited China with trying to help get the North Korea situation "under control" with the goal of denuclearising the peninsula.
A submarine missile is paraded across Kim Il Sung Square on Saturday during a military parade in Pyongyang, North Korea, to celebrate the 105th birth anniversary of Kim Il Sung, the country\'s late founder and grandfather of current ruler Kim Jong-Un.More news: Cyclone Cook: Evacuations as huge storm lashes north New Zealand
"The objective of this exercise, specifically, is to strengthen the cooperation between the U.S. and the Koreans in order to provide a combat-like scenario as real as possible", said U.S. Air Force Lt. Christopher Villanueva. North Korea routinely labels such exercises preparations for invasion.
While the North did not conduct a nuclear test, the specter of a potential test and an escalated US response has trailed Pence as he undertakes his Asian tour.
Experts say the North may soon carry out its sixth nuclear test.
Trump, in a departure from some rhetoric of his campaign, said it was very important to him to have a "strong Europe".More news: NHL Playoff Standings 2017: Current Bracket Matchups and Postseason Picture
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