South Korea says it has not received a response from Pyongyang on a summit between North Korean leader Kim Jong-un and US President Donald Trump.
In a surprise development, Mr Trump on Friday accepted North Korea’s invitation to direct talks.
South Korean officials said Mr Kim was prepared to give up his nuclear weapons.
Details on the planned talks remain vague, with no agreement yet on the location or agenda.
Analysts are sceptical about what can be achieved through talks given the complexity of the issues involved.
“We have not seen nor received an official response from the North Korean regime regarding the North Korea-US summit,” a spokesman for the South Korean Ministry of Unification said on Monday, BBC reports.
“I feel they’re approaching this matter with caution and they need time to organise their stance.”
South Korean officials are heading to China to discuss the summit with counterparts in Beijing, which is seen as the last supporter of the North Korean regime.