The North Korean accounts held in Banco Delta Asia in Macao were frozen in September 2005 at the request of the United States, which accused the Communist regime of counterfeiting and money laundering.
"South Korea has so far received no such request either from the U.S. or China, and is acting as an observer," the source said in an interview with RIA Novosti, adding that Seoul was ready to play a more active role if no resolution is found by early June, but expressed doubt, whether that would happen any time soon.
He said there is still no consensus within the U.S. administration on the kind of concessions that could be made to North Korea, while Pyongyang is not particularly interested in speeding up the process.
Earlier in May, North Korea accused the U.S. of foot dragging on Pyongyang's frozen $25 million at a time when it was ready to denuclearize.
North Korea's $25 million in BDA was unfrozen in March in an attempt to win Pyongyang's promise to close its nuclear reactor. But the fund transfer was stalled as Washington blacklisted the bank, making other banks wary of handling Korean funds and dealing with the BDA. In response, the regime delayed shutting down its Yongbyon reactor, planned for April.
The North has pledged that it will fulfill its February commitments with the five countries involved in a protracted nuclear dispute, as soon as it receives the funds.
The impoverished state has been cut off from global financial markets for several years and has used cash or complicated barter schemes to pay for supplies and services from other countries.
Pyongyang boycotted disarmament talks for more than a year over the funds and conducted its first nuclear bomb test in October 2006.
After North Korea's nuclear test in October 2006, Japan completely halted imports from the republic and closed all its ports to North Korean ships.
