North Korea threatened Japan on Thursday with "strong countermeasures" if it goes ahead with tougher sanctions over Pyongyang's reported nuclear test.
Japan and the United States are pushing for tough measures against the North, although diplomats say China opposes the more punitive parts of a draft resolution Washington wants the UN Security Council to adopt in a vote, possibly on Friday.
"We will take strong countermeasures," said Song Il-ho, North Korean ambassador in charge of diplomatic normalisation talks with Japan, according to a report by Japan's Kyodo news agency from Pyongyang.
"The specific contents will become clear if you keep watching," Song said. "We never speak empty words." Japan, arguing that Pyongyang's nuclear weapons poses a direct threat to its safety, is expected to formally approve additional sanctions on Friday, including banning imports from the impoverished communist state and blocking North Korean ships from entering Japanese ports.
US President George W. Bush, speaking after Japan announced plans for extra sanctions, said on Wednesday: "In response to North Korea's actions we're working with our partners ... to ensure there are serious repercussions for the regime in Pyongyang,"
China, the nearest North Korea has to an ally, has flatly condemned its communist neighbour and backs limited sanctions but diplomats said it sees the US approach as too stringent. "One can say that punishment isn't the goal," Chinese Foreign Ministry spokesman Liu Jianchao told reporters on Thursday, saying any sanctions would be to coax North Korea back to talks.
There has so far been no independent confirmation that Monday's explosion was in fact the result of a nuclear device. Some have speculated that even if it was, it might not have been as successful as Pyongyang claimed. North Korea has brandished the threat of more tests, calling US pressure to rein in its nuclear programme tantamount to a "declaration of war".
A UN Security Council vote on the US-drafted resolution could come on Friday, when the leaders of China and South Korea - on which Pyongyang relies for economic aid and a level of diplomatic protection - are also due to meet in Beijing.
Both countries are anxious to avoid driving the reclusive North - with its 1.2-million-strong army - further into a corner, possibly triggering instability on the Korean peninsula, which has been divided for more than half a century. Analysts question how much sway Beijing and Seoul have over North Korea, which has recently shown it is prepared to shun its main benefactors.
US Ambassador John Bolton intends to introduce formally the resolution to the 15-member Security Council members in hopes of a vote on Friday. But China is expected to insist on further negotiations, diplomats said.
The draft, backed by Japan, also calls for an arms embargo, a ban on the transfer or development of weapons of mass destruction and banning trade in luxury goods. It would freeze funds overseas of people or businesses connected with North Korea's nuclear and ballistic missile programmes.
It adds a proposal by Japan that would allow, but not require, states to bar the entry of individuals and their families connected to or supporting the North's policies on weapons of mass destruction.
The new US draft still invokes Chapter 7 of the UN Charter, which could ultimately lead to military action, and determines that North Korea's actions are a threat to international peace and security. China has called military action "unimaginable".