U.S. Ambassador to the United Nations Nikki Haley said North Korea's actions show that its leader, Kim Jong Un, is "begging for war,'' and the time has come for the Security Council to adopt the strongest diplomatic measures.
Haley told an emergency session of the Security Council on Monday that "enough is enough. War is never something the United States wants. We don't want it now. But our country's patience is not unlimited.''
The emergency session comes after North Korea detonated what it called a hydrogen bomb on Sunday.
It also comes less than a week after the council strongly condemned the North's "outrageous'' launch of a ballistic missile over Japan.
Other Security Council members, including Japan and France, are calling for further sanctions.
The council already imposed its stiffest sanctions so far on North Korea last month.
The U.N. political chief Jeffrey Feltman called North Korea's test a "dangerous provocation'' that is profoundly destabilizing for the region and the international community, and urged a comprehensive response.