A leading Japanese daily says efforts to open working group nuclear talks this month have run into difficulties with Pyongyang balking at the complete dismantlement of its nuclear program.

Quoting the South Korean government and diplomatic sources, the Yomiuri Shimbun said Monday that China had distributed a "concept paper" to the concerned parties on the agenda and procedures of the working group discussions.

The reports added that North Korea is digging its heels in over its demand for energy aid and security guarantees in return for a nuclear "freeze."

The United States is also sticking to its call for the North to completely, verifiably and irreversibly dismantle its nuclear weapons programs before any talk of possible concessions.