The tiny USA territory of Guam came under the worldwide spotlight after North Korea on Wednesday said it's studying whether to launch a missile test toward the island.
Senior US officials have also downplayed the threat of an imminent military conflict, with top US general Joseph Dunford stressing diplomacy and sanctions over war in a meeting in Seoul with South Korean President Moon Jae In on Monday.
Trump reciprocated the sentiment and suggested that the stalemate between the USA and North Korea could have had a different outcome, had he been the president in years past.
This development comes only a few days ahead of the upcoming US-South Korean military drills that are scheduled to begin next week.
"It demands a concerted effort by the United States, but with our allies and with all responsible nations".
North Korea has never carried out its threats to hit US Pacific bases or mainland.
It said the United States was ready "along with its allies, to apply the full range of diplomatic, economic and military measures" to end any nuclear threat from the North.
After several failed tests in 2016, North Korea successfully built and launched two intercontinental ballistic missiles, despite heavy worldwide sanctions. Trump, responding to a report that US intelligence indicates Pyongyang can now put a nuclear warhead on its long-range missiles, vowed to rain down "fire and fury" if challenged.
Asked if the US was going to war, he said cryptically, "I think you know the answer to that".
Kim appeared in photos sitting at a table with a large map marked by a straight line between what appeared to be northeastern North Korea and Guam, and passing over Japan - apparently showing the missiles' flight route.
Lobbing missiles toward Guam, a major USA military hub in the Pacific, would be a deeply provocative act from the US perspective, and a miscalculation on either side could lead to a military clash.
Asked about Trump's tough posture, Guam Governor Eddie Calvo said he agreed with sending a clear message to North Korean leader Kim Jong Un, who has ramped up his country's tests of missiles and nuclear bombs.
The comments, while typically belligerent, are significant because they appear to signal a path to defuse a deepening crisis with Washington over a weapons program that is seen as having the ability to fire a nuclear missile to the U.S. mainland.
After studying the plan "for a long time" and having "discussed it" with commanding officers, the North Korean leader ordered the army to be fire-ready should he and the ruling party make the decision to further demonstrate his country's military power.
The President reiterated the comments to press later in the day, saying that Kim Jong Un would "regret" making threats to attack the USA overseas territory of Guam and mainland.
Xi also reiterated his support for a nuclear-free North Korea.
The call came after Trump unleashed a slew of fresh threats against North Korea on Friday, declaring the US military "locked and loaded" and warning North Korean leader Kim Jong Un that he "will regret it fast" if he takes any action against USA territories or allies.