SEOUL, South Korea — President Trump, whose long-distance threats and insults toward North Korea have stoked fears of a nuclear confrontation, brought a message of calm and reassurance to South Korea on Tuesday, moving to bolster an anxious ally even as he missed a chance to get an up-close look at one of the world’s most dangerous borders.
Gone were the threats to rain “fire and fury” on North Korea and the derisive references to its leader, Kim Jong-un, as “Little Rocket Man” as Mr. Trump said Tuesday that he saw progress in diplomatic efforts to counter the threat from the North, adding, “Ultimately, it will all work out.”
Mr. Trump’s plans for a surprise, unscheduled visit to the demilitarized zone separating North and South Korea were foiled on Wednesday morning by bad weather, stripping him of a chance to project toughness toward the North as past American presidents have done while peering through binoculars toward a pariah state.
The White House took pains to shroud the trip in secrecy, barring reporters traveling with him from divulging it until it had ended, but as the Marine One helicopter drew close to the demilitarized zone, dense fog prevented it from landing, sending a frustrated president back to Seoul.
The aborted trip North left Mr. Trump without a powerful image to end his visit to South Korea, devised in part to turn down the temperature on tensions in the region.
After a day of private meetings and public bonding with President Moon Jae-in of South Korea, who was elected promising a shift toward dialogue with the North, Mr. Trump — who as recently as last month tweeted that direct talks were a “waste of time” — said on Tuesday that it would be in the North’s interest to “come to the table and to make a deal.”Agree
And instead of threatening muscular pre-emptive action against the North, Mr. Trump said he prayed that using military force would not be necessary.
“I think we’re making a lot of progress, I think we’re showing great strength, I think they understand we have unparalleled strength,” Mr. Trump said of the North during a news conference with Mr. Moon. Noting that the United States military has positioned three aircraft carriers and a nuclear submarine in the Pacific, he added: “We have many things happening that we hope, we hope — in fact, I’ll go a step further — we hope to God we never have to use.”
When pressed by a reporter, Mr. Trump declined to say whether he still thought negotiations with North Korea would be a waste of time, making an uncharacteristic effort to avoid a remark that might have inflamed simmering hostility.
“I don’t want to say that — I just don’t want to say that,” Mr. Trump said. “You can understand.”
His visit to Seoul was the most diplomatically challenging leg of Mr. Trump’s 12-day, five-country trip through Asia, bringing him face to face with a public and a president wary of his combative approach on North Korea. To many of Mr. Moon’s progressive supporters, Mr. Trump poses as much of a threat to peace as Mr. Kim, if not more so.
“Don’t come, Trump! You talk about war whenever you open your mouth,” a large banner read during a protest near the United States Embassy in Seoul on Tuesday. “Go away, Trump!” hundreds of labor activists and other progressives shouted in downtown Seoul, where thousands of police officers were deployed to keep security. “No Trump, no war!”
A short distance away, across a police blockade, hundreds of conservatives welcomed Mr. Trump with South Korean and American flags. South Korean conservatives are skeptical of Mr. Moon’s approach, calling it naïve. They back Mr. Trump’s hawkish view of the North, but they, too, stop short of supporting war.
“We believe in Trump!” their signs read.
Mr. Trump’s restrained tone may have an easy explanation: He has been at odds with Mr. Moon, who took office in May, about how to deal with the North, and he was eager to avoid any public demonstration of the split.
When Mr. Trump this summer threatened North Korea with pre-emptive strikes — or what his national security adviser, Lt. Gen. H. R. McMaster, warned could be a necessary “preventive war” — Mr. Moon went in the other direction. He said that he had been guaranteed a veto over any offensive military action against the North, and that he would not allow such action. War with North Korea, he assured his public, was “unthinkable.”
Mr. Trump and his aides fumed, and the president suggested Mr. Moon was practicing appeasement. The White House view is that the only way the North will relent is if it believes Mr. Trump is perfectly willing to order a strike on the country’s nuclear facilities, even if that risks hundreds of thousand of casualties.
But to let that difference in approach spill out into the open would have played right into North Korea’s hands. It has tried, over nearly seven decades, to break the alliance. So the two leaders decided to stick to common, long-range goals.
Mr. Trump’s change in tone notwithstanding, his advisers have been making the case that North Korea’s ambition is to reunify the Korean Peninsula by force, and that traditional deterrence cannot stop the North once it has a nuclear weapon capable of hitting the United States.
Many observers are skeptical of both assertions, especially in South Korea, which would suffer greatly if a pre-emptive strike on the North led to all-out war. They argue that the leaders of North Korea’s Communist government are not planning to use nuclear weapons to attack the United States or its allies, because they know that Washington would launch an overwhelming counterattack. Rather, they say, North Korea is building its nuclear weapons out of fear, hoping that the arms will protect the country from invasion — or from outside intervention, in the case of a domestic uprising — allowing the North to focus on economic development.
“The view that North Korea would start war to communize Korea doesn’t make sense anymore,” said Kim Yong-hyun, a professor of North Korean studies at Dongguk University in Seoul. “North Korea knows that if it ever uses a nuclear weapon, it means self-destruction.”
South Korean officials said they hoped that Mr. Trump’s visit to Seoul, a city of 10 million people, would bring home to him the consequences of a potential war. Mr. Moon supports Mr. Trump’s call for “maximum” sanctions and pressure, but says that those alone will never persuade North Korea to give up nuclear weapons.
American officials in the region, too, were hoping the president’s trip would help Mr. Trump gain a new perspective on how Seoul and Tokyo view the threat from up close; the regional trends affecting Asia beyond North Korea, including Chinese assertiveness; and the costs and consequences of military action, according to one American official.
From a dining hall at Camp Humphreys, where Mr. Trump had lunch with troops, to the Blue House, where he met with Mr. Moon, everything he saw on Tuesday could become a fiery battlefield in the event of a military exchange with North Korea.
But if the firsthand experience left an impression on Mr. Trump, he did not show it. At times, his tone was almost blithe. Before being briefed by American and South Korean military commanders, he said of the confrontation with the North: “Ultimately it will all work out. Because it always works out — has to work out.” Gen. Vincent K. Brooks, the American commander, wore a grim expression as he listened.
Mr. Trump also reprised his role as the American defense industry’s chief salesman. “South Korea will be ordering billions of dollars of that equipment, which, frankly, for them makes a lot of sense,” he said. “And for us, it means jobs; it means reducing our trade deficit with South Korea.”
Mr. Trump, who is scheduled to travel to China on Wednesday, added about North Korea, “It is unacceptable that nations would help to arm and finance this increasingly dangerous regime.”
But in a reminder of the challenge that Washington faces keeping even its allies on the same page, South Korea invited an 88-year-old Korean “comfort woman,” or a former sex slave for Japan’s World War II military, to Mr. Trump’s state banquet and put on the menu a dish of shrimp said to have been caught in waters near a set of disputed islets.
The sex slave issue is one of the most contentious dividing Japan and South Korea, and the islets — known as Dokdo in South Korea and Takeshima in Japan — lie at the center of a territorial dispute.
As Mr. Trump arrived in Seoul, there was renewed evidence of activity at a site in North Korea where the North has conducted underground nuclear tests. But it was unclear whether the activity suggested another imminent test or construction on a tunnel that could be used for tests.