Less than 48 hours after the Security Council voted unanimously to impose the sanctions, US diplomats were facing reservations from key Asian nations worried that tough action could provoke the unpredictable North's regime.
Meanwhile a new poll in South Korea found more people blamed the United States than North Korea for the test, underlining doubts that the harsh US stance was effective in influencing the North's behaviour.
US Secretary of State Condoleezza Rice was headed to China, Japan and South Korea later in the week while Christopher Hill, the lead US negotiator on the North, arrived in Tokyo on Monday to discuss the Council resolution.
"We want to talk about implementing the resolution," said Hill, who was to go to South Korea on Tuesday.
"We want to talk about other measures we can take to work together to make sure North Korea is not able to get the technology nor the financing to continue these programs," he said.
The Council unanimously passed Saturday's resolution, which calls on the North to give up all weapons of mass destruction and allows nations to stop cargo going in and out of North Korea to prevent any weapons trafficking.
The measure also bars heavy conventional weapons and luxury goods from being sent to North Korea, calls for a freeze in any funds connected with the North's WMD programmes, and urges it to return to disarmament talks.
But cracks in the international consensus appeared almost immediately after the vote as China, North Korea's main ally and aid provider, indicated it would be reluctant to stop and search Pyongyang's cargo.
North Korea has warned that any tough measures would be a "declaration of war," words that sent shudders across a region already unnerved by its announcement of the atom bomb test on October 9.
In neighbouring South Korea, President Roh Moo-Hyun's spokesman reiterated concern about any action that could destabilise the tense situation.
"It is not desirable if such efforts to keep the Korean Peninsula free of nuclear weapons amplify security risks and economic instability," spokesman Yoon Tae-Young said.
South Korea is also unwilling to search the North's ships for fear of sparking an armed clash with its neighbour. The two countries have remained technically at war since the 1950-1953 Korean conflict.
Despite the sanctions, Roh's government has announced it will continue with two cross-border projects that provide tens of millions of dollars to the cash-starved North -- money which critics say can be diverted to weapons programmes.
North Korea has repeatedly said it needs a nuclear weapon to deter any attack by the United States, which it says wants to topple its communist regime.
Six-nation talks hosted by China appeared to win agreement from Pyongyang last year to give up its nuclear programmes.
But the negotiations fell apart after the United States unilaterally imposed sanctions on a Macau bank to freeze North Korean accounts.
North Korea said earlier this month that it had to conduct a nuclear test in response to the US sanctions and what it called the threat of a nuclear war from the United States.
US President George W. Bush, who has made the fight against proliferation of nuclear weapons a keystone of his foreign policy, famously lumped North Korea in with Iran and pre-war Iraq as an "axis of evil."
But with fears mounting about Iran's nuclear programme, and the North having announced it has tested the bomb, critics say US policy has not worked to stop the development of atomic weapons.
A new poll by the Korea Times found Monday that 43 percent of South Koreans blame Bush's hardline stance for North Korea's test, with only 37.3 percent blaming the North Korean regime itself.
"So far, the Republican administration's North Korea policy has been a total failure," the paper said.

Copyright AFP (Agence France-Presse), 2006