Mr Bolton said a swift response to North Korea was needed
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The UN Security Council has ended talks on a new draft of a US resolution pushing for sanctions against North Korea over its claimed nuclear test.
The US wants a vote on the draft by Friday but diplomatic sources told the BBC China and Russia opposed this.
The draft targets the North's missile and nuclear programmes under the UN's Chapter Seven - which makes sanctions mandatory and may allow using force.
China and Russia are reportedly worried about how sanctions may be enforced.
They have asked for more time to consider the US proposals.
Western diplomats believe China's support for the draft resolution is essential if tough action is to be taken against North Korea, says the BBC's UN correspondent, Laura Trevelyan.
Japanese sanctions
North Korea's underground test reportedly took place at 1036 (0136 GMT) on Monday in Gilju in north-east Hamgyong province.
Russia is the only country to have confirmed that it was a nuclear explosion, amid speculation the test was not wholly successful.
North Korea has said it will take "strong countermeasures" against Japan if it goes ahead with new sanctions against the country, a senior North Korean diplomat was quoted as saying on Thursday.
"The specific contents will become clear if you keep watching. We never speak empty words," Song Il-Ho, the North's ambassador in charge of normalising relations with Tokyo, told Japan's Kyodo news agency.
North Korea's threats are part of a campaign to make the world think twice about its response to the nuclear test, says the BBC's Charles Scanlon in the South Korean capital, Seoul.
On Wednesday, Japan imposed its own tough new sanctions on North Korea, including banning all imports from the country. The sanctions are expected to be approved by the Japanese cabinet on Friday.
On Thursday, South Korea said it had not detected any abnormal radioactivity levels in its country after the alleged North Korea nuclear test.
'Swift response'
There is agreement in the UN Security Council that North Korea should face punitive measures, but countries are divided over how tough these should be.
The US wants the sanctions - which would also target luxury goods - to be brought under Chapter Seven of the UN Charter. This means they would be mandatory and ultimately enforceable by military means.
N KOREA NUCLEAR PROGRAMME
But China, Russia and South Korea have expressed varying degrees of opposition to such a resolution.
China is also reported to be unhappy about authorising inspections of cargo vessels moving in and out of North Korea in order to find weapons-related material.
Both China and South Korea are worried that such inspections could provoke military action from North Korea - a risk neither country is willing to take, our correspondent adds.
The new draft retains the call for cargo inspections but is reported to soften language in some key areas of the document.
It also includes a clause allowing nations to ban the entry or transit of people believed to support Pyongyang's weapons programme, reports say.
Mr Bolton said he hoped for a vote on Friday.
"There are still a lot of comments that have been made, and areas of disagreement, but as we've said repeatedly, we think this requires a strong and swift response," he said.
Threat of new tests
On Wednesday US President George W Bush said North Korea would face "serious repercussions" over its nuclear test claim.
He told reporters that Washington remained committed to diplomacy, but stressed that the US reserved "all options to defend our friends in the region".
If the US, UK and other governments wish to stop other countries having nuclear weapons then they should lead by example 
But North Korea appeared unwilling to make any concessions. The country's number two leader, Kim Yong-nam, has threatened more tests if the US remained "hostile".
And a statement from a foreign ministry spokesman said that North Korea was ready "for both dialogue and confrontation".
"If the US increases pressure upon the DPRK, persistently doing harm to it, it will continue to take physical countermeasures, considering it as a declaration of a war," the statement carried by state news agency KCNA said.
Our correspondent says diplomats want to act swiftly in response to North Korea's nuclear test.
They know that Iran is watching closely from the sidelines to see how North Korea is dealt with.
Next week, the Security Council is due to consider what action to take against Tehran following its failure to stop enriching uranium, our correspondent adds.