WASHINGTON — A senior U.S. official says North Korea should learn from the emerging nuclear deal with Iran that Washington is willing to engage its adversaries if it has a "credible" negotiating partner.

Sydney Seiler is envoy to long-stalled six-nation talks on North Korea's nuclear weapons program. He also cited Cuba and Myanmar as having "responded to our offer to reach out a hand to those who would unclench their fist."

But Seiler said there was no sign in two years that Pyongyang is willing to denuclearize, as its leadership seeks to develop its nuclear program despite sanctions and diplomatic isolation.

Seiler told a think tank Tuesday that the North "may not have learned any lesson" from the Iran negotiations, and if it had, "we would perhaps have seen it earlier."