"We're in a bit of a standoff at this point," said the chief U.S. delegate to the talks, U.S. Assistant Secretary of State Christopher Hill.
Hill said no progress was made Thursday because Pyongyang was demanding that it get a reactor before dismantling its nuclear program.
"The basic stumbling block has to do with the issue of providing a light-water reactor," North Korean spokesman Hyun Hak Bong said in the first comment from the delegation since the talks resumed Tuesday.
Still, Hill and other delegates said the talks would continue, with no end date set.
The United States has said giving such a reactor to the North is out of the question, given the cost and the communist nation's history of deceit over its pursuit of nuclear technology to build weapons.
The North was promised two such reactors under a 1994 deal that fell apart in late 2002 after the latest nuclear crisis erupted. Light-water reactors are believed to be less easily diverted for weapons use.
"Providing a light-water reactor is a matter of principle for building trust," said Hyun. "The United States says it cannot give us a light-water reactor no matter what. It is telling us to give up the nuclear (program) first without doing its part."
"This is a problem related to the United States' political will to get rid of its hostile policy toward us and peacefully coexist," he said.
But the North Korean spokesman added that his government still hoped to "solve the nuclear issue peacefully through dialogue."
The North has been offered economic aid, security guarantees from Washington and free electricity from South Korea in exchange for dismantling its nuclear weapons program. The South Korean offer to send electricity to the North could begin delivering power in a few years, helping alleviate chronic energy shortages that have further hampered its already struggling economy.
Hill described the reactor issue as a "nonstarter."
North Korea "not for the first time, has chosen to isolate itself," Hill said. The country "has a rather sad and long history of making the wrong decision on things."
None of the other countries at the talks, which also include Russia and South Korea, has stepped forward with an offer to foot the estimated $2 billion to $3 billion cost for building a reactor, Hill said, noting it could take up to a decade to be completed.