The US, Japan and South Korea on Friday vowed they would crack down on alleged criminal activities by North Korea, including drug smuggling and money counterfeiting.
At a meeting in Hawaii, senior government officials of the three allies also urged Pyongyang not to inflame tensions over its suspected nuclear weapons program and vowed to seek a peaceful solution to the crisis.
The trio "expressed concern over the illegal activities by North Korean entities, including drug-running, counterfeiting and discussed means of co-operating among themselves and with other countries and international organizations to stop such activities," the communique said.
The calls came in a communique issued after a regular two-day meeting of the Trilateral Coordination and Oversight Group (TCOG) in Honolulu.
The reference to the illegal activities in the final statement was believed to be the first time such allegations have been committed to paper by TCOG, apparently indicating a firming of the allies' resolve in tackling Pyongyang.
The warning came as Japan and Australia beefed up inspections on North Korean ships suspected of trafficking drugs, counterfeit cash and missile parts, items that economically hobbled Pyongyang is thought to rely on for hard currency.
And on Thursday, five Japanese citizens were arrested in Tokyo on suspicion of illegally exporting jet-mill grinding machines, which can be used in making solid fuel for missiles, to Iran in 1999 and 2000.
North Korea has denounced Japan's decision to step up inspections of its ships, a move which has the strong backing of Washington which put Pyongyang on its "axis of evil" along with Iraq and Iran.
The officials in Hawaii also tackled the thorny issue of North Korea's nuclear program after it admitted publicly for the first time on Monday that it was seeking nuclear weapons to counter a US threat to its regime.
Washington, Tokyo and Seoul -- which have been at odds over how to handle the crisis -- also warned Pyongyang not to heighten international tensions over its nuclear program.
"The three delegations urged North Korea not to exacerbate the situation," the communique said.
"[The allies] agreed to continue to seek a complete, verifiable and irreversible end to North Korea's nuclear weapons program through peaceful, diplomatic means," the three nations said.
They stressed that North Korea's ties with them and the rest of the world "hinge on its taking prompt and verifiable action to end its nuclear weapons program fully and in a verifiable manner."
The meeting came amid lingering fears of a showdown after unpredictable Pyongyang announced last year it was restarting its frozen nuclear reactors that are capable of producing weapons-grade plutonium.
Since then, Washington has made efforts to nudge North Korea back to the negotiating table, while President George W. Bush and Japanese Prime Minister Junichiro Koizumi agreed last month to consider "tougher measures" against North Korea if it escalates its nuclear threat, a stance Seoul is not keen on.
The three powers in Hawaii also insisted at the meeting that South Korea and Japan take part in future multilateral talks over North Korea's nuclear program, despite Pyongyang's earlier objections to their presence.