President Moon Jae-in leaves for Washington on Monday to meet US President Donald Trump for talks on North Korea. The meeting, which had been expected to set the tone for a historic meeting between Trump and North Korean leader Kim Jong-un, carries greater significance due to the Pyongyang government’s abrupt shift to a hard-line stance.

In a sense, the Moon-Trump discussions -- especially about the terms on which the North will denuclearize -- and North Korea’s response to their agreement might determine the fate of the denuclearization talks.

Nam Gwan-pyo, a senior security aide to Moon, said in a pre-departure briefing that the president would try to play a role as a “bridge” between the US and North Korea. He said Moon and Trump are expected to discuss ways to “guarantee a bright future for the North when it achieves complete denuclearization.”

It would be good if Moon, who in effect brokered the planned meeting between Trump and Kim, is able to continue to mediate between the two leaders.

But Moon suffered a serious setback over the past week as the North abruptly dampened ties with the South. It certainly is a big embarrassment for Moon, who held the first inter-Korean summit in 11 years with Kim and reached an agreement on denuclearization and improvement of bilateral relations.

The North’s unexpected about-turn seems to have been premeditated. It first canceled high-level talks with the South, then warned that it would “never be easy to sit face to face again with the present regime of South Korea” and more ominously, rejected the names of South Korean journalists who were to cover the shutdown of the North’s nuclear test site later this week. The three actions came one by one from Wednesday to Friday. The North Korean Red Cross also demanded repatriation of 13 North Koreans who defected to the South in 2016 after working at a restaurant in China.

It is not hard to imagine why the North is ratcheting up tension. The North is pressing the Moon government to help keep US hard-liners like national security adviser John Bolton in check. The first North Korean statement that threatened to cancel the US-NK summit focused on accusing Bolton of pushing for unilateral, unconditional denuclearization.

North Korea is sending the message to the US that it can reverse the reconciliatory mood -- as it did with the South -- with the US and even abort the meeting itself if Washington pushes too hard. That is typical North Korean brinkmanship.

All in all, the North intends to strengthen its negotiating position ahead of the US-NK summit set for June 12 in Singapore. It is obvious that Kim wants to insist on denuclearization on his own terms but obtain a strong security guarantee and generous economic incentives from the US.

For now, Trump is dealing prudently with the North. He tried to pacify the North by clarifying that he was not thinking about a Libyan model of denuclearization for the North. He even ruled out a regime change and promised economic prosperity on the level of South Korea.

The better part of Trump’s response to the North Korean threat to “reconsider the summit” was that he issued a stern warning that if the denuclearization talks collapse, the ongoing maximum pressure campaign against the Pyongyang regime would continue to be in place and it could face the same fate as Libya.

In other words, the US president is saying that Kim will be able to get everything -- a guarantee of security for his regime and the country and economic assistance -- if he agrees to acceptable denuclearization terms. If not, the North would face what Trump called “total decimation.”

That positon should be shared by all members of the international community, not least President Moon. What can never be compromised on is the complete, verifiable and irreversible dismantlement of the North’s nuclear capabilities.

The Moon-Trump meeting should be an occasion for the two leaders to reaffirm the principle and urge the North to come to the negotiation table with the genuine intention to denuclearize, which would reward it with security and prosperity.