A senior US nuclear negotiator offered a bilateral meeting with North Korean officials but was turned down, South Korean officials said.
Mr Hill offered the meeting during his recent visit to China
Christopher Hill proposed talks with North Korean negotiator Kim Kye-gwan during his recent visit to China, a Foreign Ministry official said.
But there was no response from the North Koreans to the rare US offer.
The move comes amid a deadlock in talks on the North's nuclear ambitions and tensions over its recent missile tests.
Pyongyang tested seven missiles, including a new long-range weapon capable of hitting the US, on 5 July, sparking international concern.
There has also been speculation that North Korea may be planning what is thought to be its first nuclear test.
Officials from the South Korean Foreign Ministry said Mr Hill had sent a message to North Korea offering a one-to-one meeting with his counterpart during his six-day visit to China.
"I understand that Assistant Secretary Hill made such a gesture on his own initiative to try to resume the six-party talks," said South Korean Vice Foreign Minister Yu Myung-hwan.
North Korea has repeatedly asked for direct negotiations with the US, but Washington says all talks must take place within the multilateral framework.
Mr Hill's meeting would have taken place on this basis, Mr Yu said.
The US and North Korean negotiators held a direct meeting in July 2005, but in April this year Mr Hill reportedly rejected a private meeting with Mr Kim in Tokyo.
News of the offer came ahead of a meeting on Thursday in Washington between South Korean President Roh Moo-hyun and US President George W Bush.
South Korean media have suggested the two sides are apart on how to handle North Korea.
Seoul is said to be seeking a softer approach towards Pyongyang, while the US is reportedly eyeing further economic sanctions.