Washington's point man on North Korea today hinted at more sanctions against Pyongyang over its atomic weapons programme in the wake of Iran's nuclear deal with world powers.
Glyn Davies, the US special representative for North Korea policy, said he hoped quickening diplomacy examining when to resume stalled six-party talks would bear fruit.
The talks are designed to push the reclusive state to abandon its nuclear ambitions, but have been in limbo since December 2008.
"Pyongyang's attempts to engage in dialogue while keeping its programme running are completely unacceptable," Davies told reporters after a meeting with his counterparts in Tokyo.
"If we do not see signs of the North Koreans' sincerity, if they do not act to demonstrate that they understand they must fulfil their obligations and give up their nuclear weapons, then there is more pressure that will be brought to bear on them," he said.
North Korea is currently pushing for a resumption of the six-party talks, but the United States says it must first demonstrate a commitment to denuclearisation.
US President Barack Obama's administration has repeatedly voiced frustration over its dealings with North Korea, but critics have said the issue has faded from US priorities.
Analysts have also expressed doubts over the effectiveness of the six-party framework, which critics say allows Pyongyang to make promises it feels free to renege on later.
During Davies' week-long tour of Northeast Asia, Iran agreed to curb its nuclear programme for the next six months in exchange for limited sanctions relief, in a preliminary accord led by the United States.
Davies warned that it was difficult to draw direct comparison between North Korea and Iran, but highlighted the fact that the use of sanctions led to success with Tehran.
Davies said the United States was in close consultation with China to examine the right "threshold" to allow the resumption of six-party talks, which group the two Koreas, China, Japan, Russia and the United States.
"We believe sanctions and pressure are key in sharpening choices that Pyongyang faces," he said.
"Given North Korea's continued flouting of its international obligations and international law, given its testing of nuclear devices, given its repeated threats of nuclear attack, its elevation of its nuclear weapons programmes and pursuit to its highest national priority, we will continue to keep pressure on North Korea, to keep the screws to North Korea," he said.
If North Korea fails to comply with the demands of the international community, "we will have to amp up that pressure in order to continue to try to bring home to them that this is a mistake," Davies said.
"There is still a room for diplomacy," he added.
