The talks on Tuesday between Christopher Hill and Kim Gye Gwan led to no breakthroughs, although South Korea says the two men will meet again on Wednesday.
Meanwhile, Washington is reportedly looking into unfreezing some of the $24 m locked in North Korean accounts in a Macau bank.
Commenting on Tuesday's meeting, Tom Casey, a State Department spokesman, said the US wanted to return to six-party talks "as soon as possible".
Güncelleme Tarihi: 20 Eylül 2018, 18:16
At the December talks, North Korea's envoy reportedly insisted that the US lift financial restrictions against the country as a condition to talks on disarmament.
He said the meeting "focused more on some of the follow-up to some of the proposals and ideas expressed in the last round of talks".
The six party framework brings together Japan, China, the US, Russia along with North and South Korea.
The last round of talks, held in Beijing in late December made no progress towards persuading North Korea to abandon its nuclear weapons programme and broke up without an agreement on when to meet again.
North Korea conducted its first nuclear test on October 9 last year, sparking international condemnation and UN sanctions.
Song Min-soon, the South Korean foreign minister, said on Wednesday he expected Hill and Kim to meet for a second day to discuss ways of breaking the impasse.
|The last round of six-party talks |
ended in deadlock [AFP]
Several US officials said they believed the Bush administration was now inclined to find a solution to the year-long dispute over the accounts in Banco Delta Asia (BDA), which Washington has called a "willing pawn" in Pyongyang's alleged counterfeiting and money-laundering activities.
But they stressed this would not affect UN sanctions and US laws and regulations that provide other authority for cracking down on Pyongyang's finances and weapons trade.
North Korea has cited the frozen BDA accounts as a prime reason for stonewalling six-country talks on ending its nuclear programme.
The US side meanwhile said North Korea must provide details of all of its nuclear facilities and programmes, and accept inspections from the International Atomic Energy Agency.
The United States was also said to have demanded that the North close its plutonium-producing nuclear reactor in Yongbyon and seal off underground facilities from where it conducted the October 9 test.
In 2005 North Korea signed a statement agreeing to give up its nuclear weapons programme in exchange for economic aid and security guarantees from the other five states, before proceeding with the test.
News of the Berlin talks came as a European diplomat, speaking to Reuters on condition of anonymity, said intelligence reports indicated that Pyongyang appeared to be planning a second nuclear test.
The diplomat said there was speculation the test could be timed to fall either on the birthday of Kim Jong-il, North Korea's leader, on February 16, or his late father, Kim Il-sung, on April 15.