U.S. Secretary of State John Kerry has left many here puzzled by abruptly saying that Washington is ready to sign a non-aggression agreement with North Korea.

Kerry made the statement during a news conference in Tokyo last week. Although it was attached with one condition ― the North should first decide to denuclearize and to engage in legitimate negotiations to achieve that end ― the overture came as a surprise to many.

It is because Kerry was the first U.S. official to express in public Washington’s willingness to conclude a non-aggression pact with Pyongyang.

A non-aggression treaty with Washington has been one of the North’s long-standing demands. The U.S. has thus far rejected it on the grounds that it has never concluded such a treaty with any country in the world.

Many wondered if the secretary had made the remark offhand or after much thought. In light of the fact that Kerry is a long-time advocate of dialogue between the U.S. and the North, the statement needs to be seen as reflecting his long-held beliefs.

A more important question is whether the secretary’s remark represents a change in U.S. policy. The U.S. Embassy in Seoul tried to play it down, saying it simply reaffirmed Washington’s existing policy on the North.

The embassy reminded that the U.S. had already affirmed in the Sept. 19 joint statement of 2005 that “it has no intention to attack or invade North Korea with nuclear or conventional weapons.”

Yet Kerry’s explicit statement cannot be dismissed as a simple reaffirmation of Washington’s current stance. Rather, it could be a new carrot the secretary is offering to induce the North to give up its nuclear weapons.

Yet the overture has caused some concern here, as Kerry appears to have proposed it without prior consultation with Seoul. While he is welcome to make fresh efforts to persuade the North to denuclearize, he should talk with Seoul first on his ideas.

Kerry’s idea is also not without its problems. For instance, how would the U.S. react to any provocation by the North using traditional weapons if it signed a non-aggression pact with Pyongyang upon the latter’s decision to denuclearize?

A non-aggression pact with the North is something that should be discussed after other threats it poses, such as missiles and chemical weapons, have been fully addressed.

Having said this, we fully back the secretary’s efforts to press North Korea to give up its nuclear arms. The North should realize that its policy of simultaneously pursuing economic development and nuclear weapons is doomed to fail. Nuclear weapons cannot ensure its survival.