UN Security Council members are working to overcome differences over what sanctions North Korea should face in the wake of its claimed nuclear test.
South Koreans have been avidly following news of their neighbour
There is agreement that Pyongyang should face punitive action and the US has proposed a range of tough measures.
But China and Russia oppose any sanctions which would be ultimately enforceable by military means.
Earlier, reports of a second apparent nuclear test were dismissed by senior officials in South Korea and the US.
A Japanese TV channel had said Tokyo officials were investigating reports of a further test following earth tremors in the area.
But US and South Korean officials said they had detected no seismic activity in that area.
The US has proposed a 13-point draft resolution and wants to see the sanctions brought under Chapter Seven of the UN Charter.
This means the measures would be mandatory and ultimately enforceable by military means, although the US has stressed it wants to resolve the crisis through diplomacy.
US Secretary of State Condoleezza Rice warned North Korea that it faced sanctions unlike any it had experienced before, because it had crossed "an important line" when it claimed to have carried out a nuclear test.
In an interview on US television, Ms Rice again ruled out direct talks between Washington and North Korea.
"Why are the North Koreans so insistent that there be bilateral talks?," she said.
US SANCTIONS PROPOSAL
Halting trade in material that could be used to make weapons of mass destruction
Inspections of cargo going in and out of North Korea
The ending of financial transactions used to support nuclear proliferation
A ban on the import of luxury goods
"It's because they don't want the pressure of having China and South Korea and Russia and Japan at the table too.
"They would like nothing better than to have all of the pressure be on the United States to deliver a deal."
The US has suggested there should be a ban on military trade with North Korea and stringent inspections of cargo going into and out of the country.
Japan wants to ban all countries from allowing North Korean ships to use their ports and planes to take off from or land in their territory.
Japan's ambassador to the UN, Kenzo Oshima, said negotiations on the draft resolution have become quite specific.
"Obviously we still have some difference of views and opinion with respect to some specifics that we'd like to see included," he said.
N KOREA NUCLEAR PROGRAMME
Believed to have 'handful' of nuclear weapons
But not thought to have any small enough to put in a missile
Could try dropping from plane, though world watching closely
Talks are due to resume later on Wednesday.
BBC correspondent Laura Trevelyan, who is at the UN headquarters in New York, says diplomats hope to reach agreement by the end of the week.
Russia, which like China has resisted sanctions in the past, has said it is "ready to take part in joint efforts of the interested parties to arrive at a peaceful, diplomatic settlement of the situation," the foreign ministry said.
The response of China - the country that holds the most influence over the isolated regime - is seen by many analysts to be key in moving the crisis forward.
China's United Nations ambassador, Wang Guangya, has said that North Korea should face some "punitive actions", but the response needed to be "firm, constructive, appropriate but prudent".
He said China wanted to see "some elements" of Chapter Seven in the resolution.
Only Iran, which also faces Security Council action over its failure to suspend its uranium enrichment programme - has voiced support for North Korea.
The underground test reportedly took place in Gilju in Hamgyong province at 1036 (0136 GMT) on Monday morning.