The US has accused North Korea of "begging for war" and pushed for the "strongest possible measures" on Pyongyang following its sixth and most powerful nuclear test.
As world powers scramble to react to the latest grave step in the North's rogue weapons programme, South Korea launched major live-fire naval drills to warn its isolated neighbour against any provocations at sea Tuesday morning local time.
US Ambassador Nikki Haley told an emergency meeting of the UN Security Council that Washington will present a new sanctions resolution to be negotiated in the coming days, with a view to voting on it next Monday.
"Only the strongest sanctions will enable us to resolve this problem through diplomacy," Haley told the meeting Monday called by the United States, Britain, France, Japan and South Korea.
North Korea on Sunday triggered global alarm when it detonated what it described as a hydrogen bomb designed for a long-range missile.
The underground blast had a yield of between 50 and 100 kilotons, or on average more than five times more powerful than the bomb detonated over Hiroshima, UN political affairs chief Jeffrey Feltman told the council.
Declaring that "enough is enough," Haley said incremental sanctions imposed on Pyongyang since 2006 had failed.
Leader Kim Jong-Un's "abusive use of missiles and his nuclear threats show that he is begging for war," she said.
"War is never something the United States wants and we don't want it now, but our country's patience is not unlimited," she said.