SEOUL (BLOOMBERG) - After North Korea launched an intercontinental ballistic missile, new South Korean President Moon Jae In warned North Korean leader Kim Jong Un "not to cross the red line", vowing a stern response should he step over it.
The problem is, it is unclear where that line is.
North Korea's move towards a rocket capable of reaching the US mainland would justify tougher sanctions after consultations with the US, a presidential official told reporters on Tuesday (July 4). But he added that Mr Moon's red line was an "abstract concept" for now.
On the flip side, it would be hard for Mr Moon to move quickly towards talks with Mr Kim as that is premised on a freeze in North Korea' weapons programme, said the official, who asked not be identified due to the sensitivity of the topic.
The lack of a clear plan from the new administration leaves Mr Moon, a former human rights lawyer in office since May, in danger of playing a lesser role over his reclusive, nuclear-armed neighbour. Mr Kim has already directed his recent rhetoric at the US, promising to send more "gifts" Mr Donald Trump's way.
Mr Moon will meet with other leaders at the Group of 20 summit in Germany this week, where collective condemnations are expected of Mr Kim's actions, while South Korea and the US conducted a joint missile drill on Wednesday (July 5). Meeting with German Chancellor Angela Merkel in Berlin on Wednesday, he said the pace of Pyongyang's weapons development was a concern.
Still, his attempts to sound forceful against North Korea while also urging caution against rash action, and the lack of clarity on his "red line", risk appearing wishy-washy at home.
With popularity ratings around the 80 per cent mark, expectations are high domestically for Mr Moon to improve on the prior administration, where the president was impeached.
"The ICBM test has put both Moon's popularity and his North Korea policies on a test board," said Mr Lee Jae Mook, who teaches political science at Hankuk University of Foreign Studies in Seoul.
Mr Kim's advances in weapons technology "create a lot of homework for Moon", particularly if the tensions spill over to South Korea's economy or people start to feel less safe, said Mr Kim Yun Cheol, who teaches political science at the Humanitas College of Kyung Hee University.
Mr Moon is already facing some pressure.
Mr Choung Tae Ok, the floor spokesman for the main opposition Liberty Korea Party, said that Mr Moon would end up doing "nothing" if he sticks to his dual approach of sanctions and dialogue.
Leader of the opposition Bareun Party Lee Hye Hoon, called on Mr Moon to conduct a "fundamental review" of his policies.
Just 1 per cent of those who approved of Mr Moon in a Gallup Korea poll last week said they support him for his North Korea policies, while a further 1 per cent favour him for his diplomacy.
Among those who disapproved, a combined 17 per cent said they did so for his North Korea policies, diplomacy, or a controversy over a US missile shield.
"Moon's desires notwithstanding, Pyongyang has no interest in discussing nuclear matters with the South," said Mr Ralph Cossa, president of the Pacific Forum CSIS in Honolulu. Mr Kim wants to talk with the US as "one nuclear power to another",he said.
"Moon has been willing to talk tough to keep Trump on his side, but I'm not sure he is prepared to play the kind of hardball that would be required to really bring Kim to his senses."
Just two days before the missile test, Mr Moon returned from Washington after meeting with Mr Trump. Mr Moon said the US leader had handed him the keys to lead a push against Mr Kim's nuclear ambitions, allowing him to embark on "a long journey to build an eternal peace system" on the Korean peninsula.
But Dr Shin Beomchul, a professor at the Korea National Diplomatic Academy, said the chances of inter-Korean talks are fading. "With the success of the ICBM, the North will ask for a higher level of compensation and Moon would find it difficult to meet all of the proposed conditions," Dr Shin said.
Mr Namkoong Young, who has taught inter-Korean politics at Hankuk University of Foreign Studies for more than 25 years, said one of the few choices left for Mr Moon is to stress and strengthen South Korea's alliance with the US.
Mr Moon's hope to resolve the nuclear issue through talks with Mr Kim "sounds too idealistic to me," said Mr Young.