South Korea (searchsaid Monday there is no proof that North Korea has completed a key step toward the production of nuclear weapons, although the North reportedly claimed that it has.

The statement by Yoon Young-kwan, South Korea's foreign minister, was the latest in a series of conflicting reports on North Korea's nuclear activities (search). The communist nation expelled international inspectors in December, and the United States relies mainly on satellite images for clues about what is going on at its nuclear facilities.

"No scientific data or evidence has emerged to prove that North Korea started reprocessing spent nuclear fuel rods at full scale or has completed the process," Yoon said in an interview with CBS radio in Seoul.

Yoon said South Korea and the United States were cooperating on efforts to obtain information about North Korea's nuclear activities.

South Korean media on Sunday said that North Korea had told U.S. officials in New York last week that on June 30 it had finished the reprocessing of the spent nuclear fuel rods, which yield weapons-grade plutonium (search). The claim contradicted a South Korean government report last week that North Korea had reprocessed only a small number of the rods.

South Korean media said North Korean diplomats at the United Nations headquarters made the claim. Some of the media reports cited Chang Sung-min, a former South Korean lawmaker who quoted unidentified sources in Washington.

South Korea's Foreign Ministry declined to confirm the reports, saying it was not "appropriate" to comment on contacts between the United States and North Korea.

Intelligence experts say North Korea could build several nuclear bombs within months if it reprocesses all of its 8,000 spent fuel rods. Washington believes the North already has one or two bombs.

The nuclear dispute flared last October when U.S. officials said North Korea admitted running a secret nuclear program in violation of a 1994 deal with Washington.

The United States and its allies suspended fuel shipments promised under the 1994 deal, and North Korea retaliated by expelling U.N. monitors, restarting nuclear facilities and withdrawing from the Nuclear Nonproliferation Treaty.