An envisioned civilian nuclear cooperation deal between the United States and South Korea is expected to address all of Seoul's top atomic energy priorities, including the headache of disposing of spent nuclear fuel, a State Department spokesperson said Monday.

The official made the remarks to Yonhap News Agency without providing any further specifics, such as how the agreement would address the spent fuel storage problem or if the U.S. would allow Seoul to reprocess spent fuel to reduce nuclear waste.

Winning the right to enrich uranium and reprocess spent fuel has been South Korea's No. 1 demand in more than four years of negotiations with the U.S. to revise their 1974 nuclear energy cooperation pact, known as the "123 agreement." 

Under the current pact, South Korea is banned from enrichment and reprocessing activity in exchange for U.S. technological assistance. Washington has been reluctant to cede to Seoul's demand for the right to enrichment and reprocessing due to proliferation concerns.

"Our two countries are confident that a new agreement can greatly advance our bilateral cooperation and address the ROK (South Korea)'s civil nuclear energy priorities of assured fuel supply, spent fuel management, and competitiveness in the global nuclear energy market," the State Department official said.

The spokesperson also said that the U.S. is pursuing an agreement that "reflects the ROK's status as a major global nuclear supplier and the great importance both governments place on maintaining high standards of nuclear safety and security upon which we are continuously improving, while maintaining our strong commitment to nonproliferation."

The 1974 pact had been scheduled to expire in March this year, and Seoul and Washington launched negotiations to revise it in 2010. But after failing to find a compromise, they extended the existing pact to March 2016 to buy more time for negotiations.

Now, the two sides appear close to agreement. 

In late October, the sides said in a joint statement following "two plus two" alliance talks that they made "significant progress" in the sensitive negotiations. That spurred widespread views that a deal would be possible before the end of the year.

South Korean officials have long said that they consider the year's end to be the deadline for the negotiations, considering the time needed for legislative approval and other procedures necessary in both countries to put the envisioned agreement into effect.

But a senior South Korean diplomatic source in Washington said earlier in the day that the quality of the envisioned deal is more important than its timing, suggesting that the two sides may miss the year-end deadline. 

"As we've seen in other negotiations, even if we make a lot of headway, we have to sort out some final tasks and resolving them is not necessarily easy," the source said on condition of anonymity.

"I think we're at that stage with regard to the atomic energy pact."

Though there is not much time left for the negotiations, making a "balanced and future-oriented" agreement is more important than concluding a deal early, he said.

Media speculation has been rife about the scope of the final agreement. 

One much talked-about possibility is that the U.S. could allow the South to conduct reprocessing only for research purposes while leaving other reprocessing and enrichment activities subject to advance consent from the U.S. (Yonhap)