WASHINGTON (NYTIMES) - While the two Koreas were gingerly reopening a border hotline, President Donald Trump was gleefully taunting North Korea leader Kim Jong Un about the relative size of their nuclear launch buttons.
That, in a nutshell, captures the challenge facing the Trump administration as South Korea embarks on fragile new talks with North Korea.
The United States, the South's key ally, views the overture with deep suspicion. For months, it has said that talks with North Korea would make no sense until its leader, Mr Kim, at least curbs his provocative behaviour, or at best agrees to relinquish his nuclear arsenal.
Mr Trump recently has talked about the potential for war, not a diplomatic breakthrough.
Yet the president, so accustomed to being the centre of attention, must now watch from the sidelines as these longstanding enemies open a dialogue.
The talks at first are likely to focus on North Korea's potential participation in the Winter Olympics, which are being held next month in the South Korean city of Pyeongchang.
Trump administration officials said on Wednesday (Jan 3) that they were not opposed to the idea of talks, provided that they be limited to the Olympics and that the South Koreans not make any concessions to the North that they, and the US, would later regret.
The White House plans to stay in close touch with South Korean officials to coordinate the messages going out and to review any offers coming in.
Above all, the officials said, the Trump administration will resist efforts by the North to drive a wedge between the US and its ally. North Korea, they said, has a long history of using such overtures to sow dissent between South Korea and the US, particularly at times, like now, when the countries have governments with divergent politics.
The White House also reiterated that Mr Trump would continue to defy Mr Kim, regardless of any diplomacy underway. Press secretary Sarah Huckabee Sanders defended the president's Twitter message late on Tuesday about Mr Kim in which he said, "I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!"
People should question Mr Kim's mental fitness, not Mr Trump's, said Ms Sanders.
"Our policy with North Korea has not changed," she added. "We're fully committed to continuing to apply maximum pressure and working with all of our partners in the region, including South Korea, who we have a better relationship with now than ever before."
But that relationship will be tested by the opening to the North, according to officials and outside analysts. The Trump administration already has a strained relationship with South Korea's progressive president, Mr Moon Jae In, who has called for dialogue with the North since his inauguration in May last year (2017).
After North Korea tested a nuclear bomb in September, Mr Trump said on Twitter, "South Korea is finding, as I have told them, that their talk of appeasement with North Korea will not work, they only understand one thing!"
During Mr Moon's first visit to the White House, Mr Trump delivered a harsh critique of South Korea's trade surplus with the US. Negotiating teams from the two countries are scheduled to meet on Friday (Jan 5) in Washington to begin discussing possible changes to the five-year-old Korea Free Trade agreement, which Mr Trump has derided as "not exactly a great deal".
"It's a dilemma for the administration," said Mr Michael Green, who was the top Asia adviser to president George W. Bush.
"The default position of the United States should be to support North-South dialogue," he said. "At the same time, they are understandably nervous about the Moon government, which has some members who are too breathless about the prospects for dialogue."
Mr Green said he was guardedly optimistic because the Trump administration's strategy of imposing sanctions on North Korea had shown some signs of success, which would give South Korea confidence to stick with the US.
South Korea's public, he said, also remained suspicious of the North, which he said would limit the scope of Mr Moon's diplomats to make overly generous concessions.
Diplomats said it was important that South Korea appear to be in lock step with the US. That would be easier to do, they said, if the talks remain focused on relatively narrow issues, such as security at the Winter Olympics.
"It is fine for the South Koreans to take the lead, but if they don't have the US behind them, they won't get far with North Korea," said Mr Daniel Russel, a former assistant secretary of state for East Asian and Pacific Affairs in the Obama administration. "And if the South Koreans are viewed as running off the leash, it will exacerbate tensions within the alliance."
Mr Russel and Mr Green both said that Mr Trump would be a wild card in the delicate détente.
So far, the president has shown scepticism about the opening, although he has not dismissed it. "Rocket man now wants to talk to South Korea for first time," Mr Trump tweeted on Tuesday. "Perhaps that is good news, perhaps not - we will see!"
But the president has not hesitated to weigh in with provocative tweets if he judges that events have gone badly.
Mr Trump's message about his and Mr Kim's nuclear buttons - coming on the day that the North made contact with the South - left diplomats shaking their heads.
"This is where his Twitter account can cause an inflection point in the relationship," Mr Green said. He said it would be vital for Mr Trump's national security and intelligence advisers to brief him on the diplomatic opening in a way that did not nurture his suspicions.
But the president's aides have little control over outside forces, like Mr Kim's assertion in his New Year's Day speech that he had a nuclear button on his desk, and that all of the mainland US was in range of a North Korean nuclear strike.
That was the claim that provoked Mr Trump's tweet.
"Calling his nuclear arsenal too small is not the best way to persuade him to constrain that arsenal," Mr Russel noted, referring to Mr Kim.
Referring to South Korea, Mr Russel said: "Who is going to bear the brunt of this taunt?"