Japan's PM has warned North Korea it faces increased international pressure after talks on Pyongyang's nuclear programme ended without a breakthrough.
The US envoy accuses Pyongyang of not taking the talks seriously
Shinzo Abe reaffirmed support for the implementation of United Nations sanctions agreed after North Korea carried out nuclear tests in October.
He was speaking after six-party talks ended with no date for a resumption, despite five days of negotiations.
Pyongyang's envoy warned it was likely to bolster its nuclear arsenal.
"The US is taking a tactic of both dialogue and pressure, and carrots and sticks," Kim Kye-gwan told reporters in Beijing.
"We are responding with dialogue and a shield. And by a shield, we are saying we will further improve our deterrent."
He said an end to US financial sanctions would "create a good atmosphere" for future discussion.
The talks - which involved the US, North Korea, China, South Korea, Japan and Russia - were the first for 13 months.
Chinese envoy Wu Dawei ended the negotiations 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".
Japan's leader, meanwhile, called on the international community to keep up its pressure by implementing the UN sanctions agreed after its October test.
"The international community will further increase pressure on North Korea," he told reporters.
Tokyo has imposed its own sanctions on Pyongyang, in addition to UN arms and financial sanctions agreed following the test - which have raised tensions in the region dramatically.
US treasury officials also met their North Korean counterparts on the sidelines to discuss US financial sanctions. Those talks broke up with a tentative agreement to meet again in the new year.
Kim Kye-gwan says the US must first lift its financial sanctions
US envoy Christopher Hill expressed frustration over Pyongyang's refusal to consider denuclearisation until US financial sanctions were lifted.
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."
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.