North Korea has a last chance to engage in dialogue with the outside world, South Korean President Moon Jae-in said Monday during a meeting with former U.S. leader Barack Obama, Moon’s office said.

Obama is visiting Seoul this week to speak at a forum hosted by South Korea’s Chosun Ilbo newspaper, where, earlier Monday, he said North Korea’s pursuit of nuclear weapons had “done nothing to secure the North Korean people.”

Moon later briefed Obama on his summit with incumbent U.S. President Donald Trump last week, an aide at South Korea’s presidential Blue House, Yoon Young-chan, told a media briefing.

“President Moon said he talked to President Trump about using sanctions and pressure to resolve the North Korean missile and nuclear problem, but also to use dialogue at the same time,” Yoon said.

“He said it is the last opportunity for North Korea to enter the door of dialogue.”

North Korea has been relentlessly developing its nuclear weapons and missiles to carry them since the beginning of last year, ignoring the threat of yet more U.N. sanctions and U.S. military maneuvering.

North Korea says it aims to develop a nuclear-tipped missile capable of striking the U.S. mainland in order to defend itself from what it sees as U.S. aggression aimed at overthrowing its government.

Trump called for a determined response to North Korea in his talks with Moon on Friday. Trump stressed the importance of the U.S.-South Korean alliance but took aim at Seoul over trade and sharing the cost of defense.

Yoon cited Obama as saying during the meeting with Moon that U.S. citizens and the Korean community in the United States supported the bond between South Korea and the United States.

Obama told the forum the world must send a clear message to North Korea, that security and prosperity will not come from the pursuit of weapons, according to a copy of his speech, issued by Chosun Ilbo.

“The international order depends upon the enforcement of clear rules and norms. So long as North Korea chooses to remain outside of that order, they must face the consequences.”