North Korea missed last Saturday's deadline for shuttering the reactor because of a dispute over $25 million in North Korean deposits frozen in a bank blacklisted by Washington. The funds were allegedly linked to money laundering and counterfeiting.

The owner of the bank in the Chinese territory of Macau, Stanley Au, insisted the money had been unblocked. He noted however that North Korea had made no withdrawals from his Banco Delta Asia "because they cannot transfer the money out."

"There are no banks accepting the so-called black money," Au told The Associated Press. "The only thing they can do at the moment is to take the money in bank notes out of the bank."

North Korea promised the US and four other nations in February to dismantle its nuclear programs in return for energy aid and political concessions.

Meanwhile, South Korea said it will discuss food shipments to the North, despite earlier reports that Seoul was considering halting the aid in an apparent move to ratchet up pressure on the North, which has requested 400,000 tons of rice.

"The issue of food aid will be discussed" at meetings beginning Wednesday in Pyongyang, North Korea's capital, Deputy Unification Minister Kim Jung-tae told reporters.

South Korea periodically sends rice and fertilizer to the impoverished North, but often faces criticism from conservatives here and abroad for being too lenient on its northern neighbour.

North Korea's Yongbyon reactor remained in operation Tuesday, but there was a high possibility that movement of cars and people at the site recorded in satellite photos could be linked to a shutdown, South Korea's Yonhap news agency reported, citing an unnamed intelligence official. The Dong-a Ilbo newspaper carried a similar report.

An official at the National Intelligence Service, South Korea's main spy agency, told The Associated Press they were "following and analyzing some peculiar movements" around the reactor in North Korea, without elaborating. The official spoke on condition of anonymity, citing policy.