"It was a statement intended to interest us, but not a threat," a senior US official said at a briefing.
"We made clear that any such thing like that would be an unwise choice."
The official was speaking after a two-hour one-on-one meeting between US chief delegate James Kelly and North Korean counterpart Kim Kye-Gwan Thursday.
During the talks, Kim indicated that there was some sort of power struggle within the North's regime over how to deal with the nuclear weapons issue.
"There is a separate group of people and agency willing to conduct a nuclear test, to build nuclear weapons in North Korea," he said, according to Yonhap news agency.
The report did not elaborate on who the separate group was.
"It is not an easy job to dissuade them to give up the nuclear weapons development. So we need justification and reasoning to convince them," Kim reportedly said.
The US official said that in the talks North Korea again denied it had a urnaium-based nuclear program, and had been told it must come clean before aid can flow to the improverished nation.
The North Koreans denied "several times" during the talks North Korea that they had a uranium program, the US officials, while further reiterating the US stance that the alleged uranium program "has to be a part of the resolution of the issue."
"We have no plans to modify our proposals especially as we have gotten back no comments from the North Koren side."
He said North Korea had called the US plan "constructive" and was researching it carefully.
The US plan calls for a step-by-step dismantling of North Korea's plutonium and uranium weapons programs in return for aid and security guarantees and easing of its political and economic isolation.