US President Donald Trump said Tuesday denuclearization of North Korea will start “very quickly” after signing an agreement with North Korea’s leader Kim Jong-un at a historic summit in Singapore.

“We‘re starting that process,“ Trump said in response to a question about denuclearization of North Korea after meeting with Kim at the resort island of Sentosa in Singapore. The process would start ”very quickly,” he added.

The remark came after the first-ever US-North Korea summit aimed at resolving decadesold hostilities and nuclear standoff. The two leaders held a series of bilateral talks, including a one-on-one meeting in the absence of their aides.

But challenges appear to loom over what could be an arduous process of ridding North Korea of its nuclear arsenal that Pyongyang has spent decades building despite harsh international sanctions.   

Further negotiations are expected to follow as early as next month over thorny issues -- such as detailed terms and a timeline of North Korea’s denuclearization process, which would involve the complicated process of verification and inspection.

Washington had been insisting the North surrender its weapons in a complete, verifiable and irreversible fashion -- until Trump and his aides lowered their expectation as the summit approached.

“Wouldn’t it be wonderful if we walked out and everything was settled all of a sudden from sitting down for a couple of hours? No, I don’t see that happening. But I see over a period of time,” said Trump earlier this month after meeting Kim Jong-un’s top aide Kim Yong-chul in Washington.

Pyongyang, for its part, has balked at the idea of unilateral disarmament and instead called for a “phased and synchronized” denuclearization, an approach that Trump denounced as a “complete failure” made by the previous administrations.

Pyongyang also called for denuclearization of “the entire Korean Peninsula,” a phrase widely interpreted as a demand for the US to scale back its joint military exercise with South Korea, deployment of strategic assets and even nuclear umbrella over South Korea and Japan.

In order to translate the summit agreement into specific implementation, the US and North Korea should come up with a detailed timeline about what can be “front-loaded” in the early phase of a lengthy denuclearization process, experts said.

From the truce village of Panmunjeom and the Ritz Carlton Hotel in Singapore, the two sides huddled at each other to work out the terms of denuclearization, but reportedly failed to make significant headway. 

While the details of the talks were not released to the public, the negotiators appeared to tackle the one issue that could resolve the mistrust over past denuclearization talks: What immediate measures should be taken to ensure sustained implementation?

A good starting point would be North Korea’s agreement to dismantle some nuclear infrastructure within the next six months and declare full accounting of all nuclear materials within a few months, said Michael Mazarr, associate director of the strategy and doctrine at the RAND Corporation. 

At the same time, North Korea should reiterate its previous commitment to full denuclearization within a defined time period and keep up with its moratorium on long-range ballistic missile and nuclear weapons tests, he added.

“The main question is Kim Jong-un’s level of seriousness,” Mazarr said. “The great risk is that Kim badly botches his meeting with Trump, other North Korean officials seem to be stalling, and the US delegation gets the sense they are being taken advantage of.”

By Yeo Jun-seok (jasonyeo@heraldcorp.com)