South Korea and the United States began extended negotiations Monday on renewing their civilian nuclear pact, with Seoul pushing for the right to produce its own nuclear fuel.
The current accord, signed in 1974, had been due to expire in 2014, but was extended in April for two years after failing to make progress on the South's demand to reprocess spent fuel rods.
The South is seeking to lift the ban in a bid to feed its nuclear reactors and tackle its worsening power shortage, with Washington balking at the idea based on proliferation grounds.
Reprocessing creates stockpiles of separated plutonium that can then be enriched to weapons grade fissile material.
Park Ro-Byug, Seoul's chief negotiator for the talks, hinted that the United States could afford to provide some leeway, given that the US-South Korea alliance is a "linchpin" for peace and stability in Northeast Asia.
"I hope that the status of the linchpin role would be reflected in revising our agreement," Yonhap news agency quoted Park as telling Thomas Countryman, US Assistant Secretary for International Security and Non-proliferation.
Countryman said Washington was "committed to finding technical and economic solutions that enhance the relations," according to Yonhap.
South Korea has proposed pyro-processing, a new technique considered less conducive to proliferation as it leaves separated plutonium mixed with safer fissile materials.
Seoul argues that it needs to produce its own nuclear fuel to feed the 23 reactors that provide one-third of its energy needs and to deplete stockpiles of spent fuel rods which it says are reaching full capacity.
But the issue of allowing the South to produce its own nuclear fuel has become more vexed in the light of North Korea's advancing nuclear weapons programme.