The United States has dismissed a proposal from North Korea for mutual disarmament talks.
Mr Hill is the US representative at the six-party talks process
The chief US negotiator, Christopher Hill, said the offer was not helpful and not serious.
Pyongyang withdrew indefinitely from six-nation talks on its nuclear status in February.
On Thursday, it said the focus of any future talks should no longer be on the North alone, but on regional disarmament by all parties involved.
Mr Hill said that if the North Koreans wanted to make "sarcastic" statements, they should come back to the talks and make them there, and not put out what he called "silly" press statements.
The BBC correspondent in Seoul, Charles Scanlon, says the exchange underlines the width of the gulf between the two sides.
Until now, North Korea has been demanding security guarantees and economic assistance in return for a nuclear freeze. It now seems to be aiming for a much more ambitious outcome, our correspondent says.
A North Korean foreign ministry spokesman said on Thursday that Pyongyang had only felt compelled to build its own arsenal because of the threat from the US.
"The US keeps many tactical nuclear weapons in South Korea on a permanent basis. And it is ceaselessly shipping nuclear strike means there," the spokesman said.
"The US claims that if the DPRK [North Korea] dismantles its nuclear weapons first, it will be given 'collective assurances for security' and get a 'benefit'. This is, however, nothing but a gangster-like logic urging the DPRK to disarm itself and yield to the US domination."
He added that because Pyongyang now possessed nuclear weapons, rather than just the means to make them, the talks' emphasis should change.
"Now that the DPRK has become a full-fledged nuclear weapons state, the six-party talks should be disarmament talks where the participating countries negotiate the issue on an equal footing," he said.
Since 2002, three rounds of discussions involving the US, Russia, the two Koreas, Japan and China have sought to ease tensions on the peninsula, with little success.
In February, North Korea said it was pulling out of the process, claiming it was furious that US Secretary of State Condoleezza Rice had branded it an "outpost of tyranny".