They had orginally been due to wrap up on Wednesday.
Instead Pyongyang has said no discussions will take place until it has seen the money transferred from Macau to a bank in Beijing.
The delay prompted the chief US envoy to give warning that a chance to press forward with disarmament plans was being lost.
"There has been a real opportunity cost to this delay," Christopher Hill told reporters.
"They've not completed the transfer, and until they do that the North Koreans have made clear they're not prepared to engage on the substantive discussions."
Chun Yung-woo, the South Korean envoy, also expressed frustration with the delays.
"If it's not resolved, I don't know why we should just waste our time waiting for the obstacle to be cleared," Chun said of the banking issue.
He said it was unclear how long it would take for the money to be transferred as North Korea wants.
On Monday the US envoy said Washington had agreed to allow the transfer of North Korean funds from the Macau-based Banco Delta Asia to an account at the Bank of China in Beijing.
|The talks had been intended to wrap |
up on Wednesday [Reuters]
The announcement had raised hopes that a main sticking-point in negotiations had been removed.
The funds had been frozen by the US on suspicion that they were connected to alleged North Korean money-laundering activities.
But on Tuesday the North Korean delegation said it would not take part in any further discussions on its nuclear programme until it had confirmed that the funds had been credited to the Beijing account.
The six-nation meeting in Beijing - bringing together envoys from the US, Russia, China, Japan and the two Koreas - had been intended to build on a landmark deal last month giving North Korea 60 days to shut down its main reactor and plutonium processing plant in return for energy aid and normalising relations.