Lim Sung-nam, South Korea's chief negotiator at the nuclear talks, made his comments after returning from a two-day visit to Beijing, the Yonhap News agency reported.
The talks on the North's denuclearization broke off in late 2008 after North Korean officials walked out to protest sanctions against their country for its nuclear and missile tests.
The participants in the six-nation talks are North and South Korea, China, Japan, Russia and the United States.
In China, Lim met with his counterpart, Wu Dawei, and other senior officials, Yonhap said.
"During the talks [in Beijing], we agreed to make joint efforts to swiftly reinvigorate the process of efforts to resume the six-party talks," Lim said.
North Korea is has been in official mourning since the death last week of its leader, Kim Jong Il. The country's official media have been saying Kim's youngest son, Kim Jong Un, believed to be in his late 20s, would be the successor, although not much is known about him.
Lim said he and Wu exchanged views on the situation in North Korea and agreed to make joint efforts to help the North maintain stability, the report said.
Prior to Kim's death, there had much diplomatic effort to restart the talks. Yonhap said North Korea also had been expected to announce agreement with the United States to suspend its uranium enrichment program and accept U.N. nuclear monitors in exchange for food aid.