“We have to make the most” of the opportunity, South Korean Foreign Minister Kang Kyung-wha told the BBC.
The two Koreas earlier agreed to march under a “unified Korea” flag at next month’s Winter Olympics in the South.
The talks come as the US and its allies vowed to keep pressure on the North.
On Wednesday US Secretary of State Rex Tillerson said sanctions were “really starting to hurt”, expressing confidence that the pressure would eventually force the North to the negotiating table over its nuclear and ballistic missile programmes.
Also on Wednesday, Japanese Foreign Minister Taro Kono said the world should not be blinded by Pyongyang’s recent “charm offensive”.
“It is not the time to ease pressure or to reward North Korea,” Mr Kono said, Reuters news agency reported. “The fact that North Korea is engaging in dialogue could be interpreted as proof that the sanctions are working.”
Ms Kang told the BBC: “I think we understand North Korea better than anybody, having dealt with North Korea for decades, having had series of discussions off and on.
“We haven’t had any significant engagement in the recent past – but this is an opportunity.
“You can have all kinds of theories of why there are here (at the talks). There are, obviously, calculations going on the part of the North Korea decision-makers as to their actions.
“But in the end we have to make the most of it.
Ms Kang also said South Korea and its allies were “very much on the same page” regarding the longer term – the denuclearisation of the Korean peninsula.
And the foreign minister said Seoul wanted more humanitarian aid to be sent to North Korea as sanctions were beginning to take effect. (Courtesy BBC)