South Korea and the United States may miss the year-end target of renewing their nuclear accord as both sides remain divided over several issues, a ranking Seoul official said Wednesday.

Seoul and Washington are in the final stage of revising the 1974 accord over Seoul's civilian nuclear energy use, also known as the "123 agreement."

South Korea is hoping to win the right to enrich uranium and reprocess spent nuclear fuel to address the headache of growing nuclear waste. But the U.S. has been reluctant to do so, apparently due to possible negative impact on its global nonproliferation campaign amid concerns over North Korea's nuclear weapons program.

Following negotiations for over four years, the two countries hailed the "significant progress" in talks for the renewal of the pact at a meeting of their foreign and defense ministers in October. But speculation has been growing that the deal is not likely to be reached within this year.

"The two sides are making efforts to make a future-oriented and strategic cooperative scheme. As there are some points that have not been addressed, it is hard to predict the timing for the conclusion (of the new accord)," the official said, asking not to be named.

He said that it may be difficult for the two to complete the talks within this year, adding that Seoul and Washington have been in consultations to adjust the remaining unresolved matters.

"With a goal of making an advanced and mutually beneficial accord, the government is doing its best to the last minute, not restrained by a timing of the deal conclusion."

South Korea has been seeking to renew the accord in a bid to meet growing energy demand at home and help its exports of nuclear power plants. Seoul wants a nuke deal that can guarantee its autonomy in its civil nuclear use to some extent.

The main sticking point of the accord negotiations is whether Seoul can be allowed to use pyroprocessing technology, a reprocessing technology considered to pose fewer proliferation risks as it leaves separated plutonium mixed with other elements.

South Korea has wanted to use the technology as it can help ease the nauseating issue of nuclear waste disposal in a country small in territory.

Under the current nuke deal, South Korea must win permission from the U.S. case by case whenever it tries to tinker with nuclear materials and technology.

Since the 1980s, Seoul has been allowed to seek overall approval from Washington every five years, but there are still lots of inconveniences and limitations for South Korea to deal with nuclear fuel under the current pact.

The nuke accord was supposed to expire in March, but the two countries agreed to extend it by two years to March 2016 in order to buy time for further negotiations.

It is widely said that the deal needs to be reached within this year, given the domestic process for ratification and implementation in Seoul and Washington. (Yonhap)