As proved by MacroGeo, until a couple of months ago the Trump administration didn’t want to make war to North Korea but only to increase pressure on Kim Jong-un, especially through China, to get rid of Pyongyang’s burgeoning nuclear program.
Washington, however, is becoming more convinced by the minute that a military attack is the only way to pursue its strategic goal.
The United States cannot live with North Korea potentially being able of bombing America’s west coast and it feels it needs to act before such a dreadful scenario becomes reality. Most likely within the next year or so, unless Kim Jong-un abandons his nuclear ambitions altogether - a highly improbable event at this point.
Nevertheless, before attacking North Korea Washington needs to reassure China and persuade South Korea.
In particular, the US has to reassure Beijing that it would only target North Korea's nuclear installations without trying to dismantle the regime. China shares America’s interest in preventing Pyongyang’s from becoming a full-fledged nuclear power, but it also wants Kim Jong-un to stay in power, as a different regime or a unified Korea would put American soldiers on China’s border.
Moreover, the US needs China’s intelligence to thoroughly map North Korea’s nuclear sites, as Beijing’s assessment is considered to be the most accurate in the world (although flawed as it is).
Even more importantly, the White House needs to persuade Seoul that the price in terms of human lives caused by a war against Pyongyang would be worthwhile. If struck, Pyongyang would certainly retaliate by bombing Seoul, possibly causing thousands of victims, but if the US attack proves successful – the Americans have been telling their counterparts - South Korea would be then freed from a looming nuclear threat.
Necessary maneuvers that only if carried out would bring the US and North Korea closer to war. Otherwise, war remains a costly last resort.