State Department spokesman Mark Toner said they were calling for the North to comply with its international obligations and refrain from a launch using ballistic missile technology although he conceded there was no sign Pyongyang was willing to listen.
"All three countries also affirmed that if North Korea does, in fact, proceed with a launch, we would seek action by the U.N. Security Council, but I'm not going to get into what that might be," Toner told a news briefing, although he added that "there's always ways to toughen enforcement of sanctions."
The council condemned a failed North Korean launch in April and ordered seizure of assets of three North Korean state companies linked to financing, exporting and procuring weapons and missile technology.
Two U.S. officials said Wednesday that the Navy has begun moving several ships into the western Pacific in preparation for the planned launch of a long-range rocket by North Korea.
The officials said shifting the ballistic missile defense capable ships into the region is part of a routine process aimed at reassuring U.S. allies there. The officials spoke on condition of anonymity because they were not authorized to speak publicly about ship movements.
They said no more than three or four ships are being repositioned.
It was third time in six years that the Security Council imposed sanctions against North Korea. The council blacklisted eight entities six trading companies, a bank and the General Bureau of Atomic Energy and five individuals after nuclear tests in 2006 and 2009.
Under Security Council resolutions, nations are also barred from buying or selling weapons with North Korea, a key source of revenue for its authoritarian regime.
Winning the support of Russia and China, North Korea's main ally and economic partner, will be key to the world body's endorsing any further punishments.