TOKYO — Secretary of State John Kerry said Sunday that the United States was prepared to reach out to Kim Jong-un of North Korea if he made the first move to abandon his nuclear weapons program.

“We need the appropriate moment, appropriate circumstance,” Mr. Kerry told reporters in Tokyo.

While he did not say specifically what steps would be needed, according to the long-standing United States position they might include a public commitment to denuclearization and such measures as halting the production of nuclear material, refraining from testing missiles and ceasing threats to attack its neighbors.

Over the past week, there has been considerable attention on the United States’ vows to militarily defend its Asian allies and its warning that North Korea should forgo a test firing a Musudan medium-range missile.

But the United States has also postponed tests of an intercontinental ballistic missile and toned down its statements in recent weeks to try to create an atmosphere in which talks with North Korea might begin, a theme that Mr. Kerry emphasized Sunday.