With his public alarmed by President Trump’s recent threats to North Korea, President Moon Jae-in of South Korea issued an unusually blunt rebuke to the United States on Tuesday, warning that any unilateral military action against the North over its nuclear weapons program would be intolerable.

“No one should be allowed to decide on a military action on the Korean Peninsula without South Korean agreement,” Mr. Moon said in a nationally televised speech.

As a candidate for the presidency, Mr. Moon, a liberal who took office in May, said he would “say no to the Americans” if necessary. But he has aligned South Korea more closely with its military ally than many had expected. Though he suspended the deployment of a United States missile defense system opposed by China, he reversed that decision last month after North Korea tested two intercontinental ballistic missiles.

But President Trump’s threat to bring “fire and fury” to North Korea, along with other statements from American officials about the possibility of war, has unnerved many South Koreans and put pressure on Mr. Moon to live up to his campaign promise. “Our government will do everything it can to prevent war from breaking out,” he said in his speech Tuesday.

Bottom line: The only condition, at present, under which a U.S. president would not first consult with, and get approval from, a South Korean leader before launching a preemptive strike against North Korea would be if Pyongyang were to launch an attack against U.S. and South Korean forces, installations or cities. That could change, however, if U.S. intelligence concludes with a high degree of confidence that Pyongyang has deployed a functional, nuclear-armed ICBM capable of hitting American cities. Trump and his nationl security team have repeatedly stated the U.S. would not allow that.

At this point, these comments from Moon appear to be more aimed at placating South Koreans than representative of a serious change in foreign/military policy.