Former U.S. Defense Secretary Leon Panetta said the goal of talks with North Korea should be to establish conditions that let Kim Jong Un keep some nuclear weapons within internationally determined limits.

“Progress needs to be made to make sure that we reduce their nuclear stockpile, that we have some kind of limitations imposed on North Korea in terms of testing, in terms of missiles,” Panetta told Bloomberg Television on Thursday. “That is, we make it clear that even though they may ultimately retain some of their nuclear weapons, that they are going to have to join all of the civilized nations in providing limitations on their nuclear capability.”

“That is I think the ultimate goal here,” said Panetta, now chairman of the Panetta Institute for Public Policy.

Panetta was speaking as President Donald Trump kicked off a second day of meetings with Kim in Hanoi, in an effort to advance nuclear talks that have largely stalled since their first summit in June. The two sides are expected to sign a joint statement later Thursday to improve relations and build on their earlier agreement to “work toward the complete denuclearization of the Korean Peninsula.”

Panetta, who also led the Central Intelligence Agency under former President Barack Obama, was echoing a point made by some in the diplomatic community that the U.S. should accept that North Korea’s nuclear weapons program has progressed too far to expect Kim to give it up entirely.

Panetta said it might be necessary to resume multilateral talks, if Trump is unable to convince Kim to reduce his nuclear stockpile. Six-party nuclear talks from about a decade ago included the two Koreas, China, Japan, Russia and the United States.

“If we have some concrete steps that show North Korea is going to take some steps toward denuclearizing, then I am not so sure that it is necessary to engage in six-party talks,” he said. “If on the other hand they don’t make progress on that issue, and it looks like we are simply going to extend this relationship — though it is a good relationship, it’s not going to accomplish anything — then it may necessary to consider whether or not we are going to renew the six-party talks.”