The United States on Tuesday demanded that the UN Security Council respond "credibly" to anyrocket launch by North Korea which would breach international sanctions.

Susan Rice, US ambassador to the United Nations, said the major powers had already held informal talks on the looming event and that 15 UN Security Council members agreed it would be a "provocative act" by the nuclear-armed state.

"The council will need to convene and to respond credibly" to a launch, Rice told reporters.

"It is clear that any launch by North Korea using ballistic missile technology -- which is what this is -- would be a blatant violation of Security Council resolutions 1718 and 1874," Rice said.

The UN resolutions condemned and imposed sanctions over previous North Korea rocket launches and nuclear tests.

"There is no disagreement among members of the council that this is a provocative act and an act that the North Koreans should refrain from undertaking," Rice said.

"If they don't, it will be them that are increasingly isolated," Rice added, saying the reclusive state would lose "as they have in the past when they have taken steps that are ill-conceived, provocative and in violation of their international violations."

Nuclear-armed North Korea is putting the finishing touches to a ballistic rocket launch, which it says will take up a satellite into orbit. The operation, which the North says is to mark the 100th anniversary of its founding leader, has caused widespread concern.