On the eve of the UFG drills, North Korea said the USA was "pouring gasoline on fire".
The war games set to begin Monday may hold more potential to provoke than ever, given President Donald Trump's "fire and fury" threats and Pyongyang's as-yet-unpursued plan to launch missiles close to Guam.
"The joint exercise is the most explicit expression of hostility against us, and no one can guarantee that the exercise won't evolve into actual fighting", said an editorial carried by the North's official Rodong Sinmun newspaper.
In addition, Neutral Nations Supervisory Commission observers will monitor the exercise to ensure it is in compliance with the Armistice Agreement for the Restoration of the South Korean State (1953), it said.
The North later said it was holding off firing towards Guam, while it waited to see what the United States would do next. His address was preceded by a heated war of words between the United States and North Korea with both sides constantly stepping up their threats.
North Korea is a highly secretive nation and predictions of what it will do next are often little more than conjecture. It has long sought to develop a nuclear-tipped missile capable of hitting the USA mainland.
"North Korea must at least end additional provocations to create the mood for dialogue".
Around 17,500 U.S. troops will participate in the drills - a cutback from a year ago.
Still, the fact that the exercise has been scaled down from last year's, with fewer USA soldiers joining this year's drill, raises concerns that there could be a different plan brewing within Washington. "The Kim (Jong-un) regime (of North Korea) possesses nuclear, biological and conventional weapons capable of raining destruction down on millions of civilians and tens of thousands of US service members in South Korea, Japan and Guam".
Azarenka pulls out of US Open over childcare issue
Open is if she left her child behind in California, which she was not willing to do. She also said the only way she could play in the U.S.
During last year's drills, the North successfully test-fired for the first time a submarine-launched ballistic missile ruler Kim Jong Un then praised as the "success of all successes".
The United States had been conducting regular "command and control" drills in the years following the 1950-53 Korean War, but combined exercises with the South Korean military following the failed raid, in which all but two of the North Korean commandos were killed.
Still, he said, this year's drills can avoid "unusual or unusually provocative" moves.
But others think the North might use the drills as an excuse to conduct another ICBM test or maybe even act on its threat to lob missiles into the waters near Guam.
"This right now is an exercise to make certain that we're ready to defend South Korea and our allies over there", Mattis told reporters en route to Jordan, according to a transcript released by his office.
"North Korea is probably looking at all the cards it has to maximize pressure against the United States, and the drills provide a good opportunity to do it", Cheon said.
North Korean media reported on Tuesday that Kim had delayed the decision on firing four missiles towards Guam, home to a vital USA air base and Navy facility, while he waited to see what the United States did next.
North Korea is issuing fresh threats against the United States as a 10-day computer-based military exercise gets under way on the Korean peninsula.
His comments about averting war echoed similar statements he made Tuesday that only South Korea could give consent to initiate any conflict with the North.