South Korea expects talks on ending North Korea's nuclear weapons programs to resume this month and has called on Pyongyang to set a firm date to return to the table.
Diplomatic hopes were raised after North Korean leader Kim Jong-il told a South Korean envoy last month Pyongyang could rejoin the six-party talks in July if the United States met certain conditions, such as showing respect.
"A lot of effort has been made to create favorable conditions for the North's participation in the six-party talks. We believe North Korea knows that, and we expect the resumption of the talks in July," Foreign Minister Ban Ki-moon told reporters.
He said Secretary of State Condoleezza Rice's trip to East Asia, which is scheduled to start on Friday, would add momentum to resuming the talks.
North Korea said in February it possessed nuclear weapons and was boycotting the talks that includes the two Koreas, China, Japan, Russia and the United States.
A series of contacts by Seoul and Washington with Pyongyang's envoys in past weeks have fueled the expectation that it was now a matter of time before the North announced its return to the talks that have been stalled for a year.
On Monday, Japan's foreign minister said he did not share that optimism.
"In some quarters there is a very optimistic view and they probably have their basis for that, but the Japanese government is neither extremely optimistic nor extremely pessimistic," Foreign Minister Nobutaka Machimura told Reuters in an interview.
Asked how long Japan and other countries were prepared to wait, he said: "Soon, we will reach the limits of our patience."
A prominent South Korean analyst on North Korea's security strategy also said it was too optimistic to anticipate a quick resumption of the talks and the North agreeing to a negotiated settlement on ending its nuclear programs.
"At every step of the way in the six-party process, the outlook just hasn't been all that bright," said Kim Tae-woo, an expert on North Korea's weapons proliferation at the Korea Institute of Defense Analyzes, a think tank in Seoul.
"North Korea is always going to want the means to maintain its current regime," he told a parliamentary hearing on Tuesday.