Six-party talks on the dismantling of North Korea's nuclear programme have ended without any real breakthrough.
Kim Kye-gwan says the US must first lift its financial sanctions
Despite five days of negotiations in Beijing, the talks broke up and no date for a resumption has been announced.
US envoy Christopher Hill expressed frustration over Pyongyang's refusal to consider denuclearisation until US financial sanctions were lifted.
His Pyongyang counterpart Kim Kye-gwan said lifting sanctions would "create a good atmosphere" for future discussion.
He also warned that North Korea was likely to bolster its nuclear arsenal, not reduce it.
"The US is taking a tactic of both dialogue and pressure, and carrots and sticks," he told reporters.
"We are responding with dialogue and a shield. And by a shield, we are saying we will further improve our deterrent."
The talks - which involved the US, North Korea, China, South Korea, Japan and Russia - were the first for 13 months.
They came two months after North Korea sparked international condemnation by testing a nuclear weapon.
Chinese envoy Wu Dawei ended the talks with a statement that simply reaffirmed an agreement from September 2005 that the North would agree to disarm in return for aid and guarantees of security.
Mr Wu said the six nations would "reconvene at the earliest opportunity".
Hopes of a breakthrough had faded by Friday, despite reports mid-week that the US had offered an incentives package that built on the agreement of September 2005.
US treasury officials also met their North Korean counterparts on the sidelines to discuss the financial sanctions. Those talks broke up with a tentative agreement to meet again in the new year.
Mr Hill said the point of the talks had been denuclearisation, and accused the North of failing to take the issue seriously.
"When the [North] raises problems, one day it's financial issues, another day it's something they want but they know they can't have, another day it's something we said about them that hurt their feelings," he said.
"What they need to do is to get serious about the issue that made them such a problem... their nuclear activities."
Christopher Hill accuses Pyongyang of not taking the talks seriously
Japan's Prime Minister Shinzo Abe called on the international community to keep up its pressure on North Korea by implementing the UN sanctions agreed after its October test.
North Korea took a defiant stance when the talks opened on Monday, insisting it was unconcerned if other countries did not accept its newly-acquired nuclear status.
It insisted from the start that it wanted to see US financial sanctions lifted before it would consider the issue of its nuclear programme.
Pyongyang walked out of the talks 13 months ago after the US blacklisted a Macau-based bank containing large sums of North Korean money.
Washington accused the bank of involvement in alleged money-laundering and counterfeiting activities by Pyongyang.