Cho Hyun-dong, South Korea's deputy envoy for multilateral nuclear talks, met this week with U.S. officials ahead of the annual meeting for members of the Association of Southeast Asian Nations.
A senior diplomat told South Korean news agency Yonhap both sides stressed the importance of transparency from the North Koreans.
"While South Korea and the U.S. remain open to engagement with North Korea, we remain firm in our shared stance that North Korea must take actions to regain trust and demonstrate its sincerity," the diplomat said on condition of anonymity.
Pyongyang placed a moratorium on nuclear and long-range missile tests early this year in exchange for food assistance from the United States. That deal collapsed in April, however, when North Korea tried to send a long-range rocket into orbit.
Similar efforts in 2006 and 2009 coincided with the testing of nuclear devices by the North Koreans.
The diplomat added dialogue was the best course of action for security on the Korean Peninsula. Back channels would remain open, though there are no plans for direct bilateral negotiations between Seoul and Pyongyang.