Multilateral talks among the two Koreas, China, the United States, Russia and Japan stalled in 2009. North Korea in February conducted a nuclear test, its third since 2006.
Evans Revere, a senior fellow for Northeast Asian studies at The Brookings Institution, said Washington needs to accept North Korea won't abandon its nuclear weapons program.
In a 25-page report published Thursday, Revere said Washington should remain open to talks if they offer a "serious prospect" of creating a nuclear-free Korean Peninsula.
Washington has said it wants nuclear assurances from North Korea before it sits down at the negotiation table.
Revere's report, in the "lessons learned" section, says there's been little progress made by U.S. diplomatic efforts.
"The efforts of several U.S. administrations over almost two decades have brought us no closer to the goal of ending North Korea's nuclear and missile challenges," the report said.
"Indeed, by any objective measure, those programs now pose a greater current and potential threat than ever. The breakdown of the Six-Party Talk and the collapse of U.S.-[North Korean] bilateral efforts means there is no diplomatic mechanism in place today that offers any prospect for slowing or stopping the North's [weapons of mass destruction] programs. The road to further development of these programs by North Korea is now wide open, and Pyongyang is taking it.
"The United States has pursued engagement and disengagement; dialogue and confrontation; diplomacy and pressure; threats and concessions; and soft and hard lines. Nothing has worked," the report said.
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