Ahead of a potential summit between Donald Trump and Kim Jong-un, their negotiators are trying to hash out details over an array of hitherto intractable issues, including denuclearization methods, timelines and security assurances for the isolated regime.

Another key point of bilateral negotiations is verification of the North’s denuclearization process, a tough issue that impeded past negotiations.

“(Former U.S. President) Ronald Reagan once said, ‘Trust but verify,'” Michael Raska, assistant professor at the S. Rajaratnam School of International Studies of Nanyang Technological University in Singapore.

“In other words, while trust is a necessary condition for a diplomatic engagement, it’s the verification that matters,” he added.