The United States repeated concerns Thursday over North Korea's weapon exports, saying it would ensure that aid to the impoverished Stalinist state was not diverted to beef up its missile and nuclear programs.

North Korea's weapons and weapons technology exports "is a real source of concern" to Washington as well as the international community, especially after Pyongyang declared itself a nuclear weapons state, State Department spokesman Sean McCormack said.

He spoke as Japan proposed a resolution to the UN Security Council urging members of the world body to prevent the transfer of financial resources, items, goods and technology that could contribute to Pyongyang's missile and other weapons programs.

North Korea drew international condemnation after it test-fired Wednesday seven missiles, including a new long-range Taepodong-2 which could theoretically reach US soil.

Assistant Secretary of State Christopher Hill will discuss concerns over North Korea's missile and nuclear programs during his current trip to China, South Korea, Japan and Russia, McCormack said.

The discussions would include "how to ensure that they are not able to benefit in any way from assistance from the outside in developing those programs; and also how to ensure that that technology, that know-how … is not proliferated," McCormack said.

Washington has labelled Pyongyang a leading global proliferator of missiles and missile technology. The cash-strapped state has refused to stop missile exports, a major source of hard currency earnings.

"Certainly, North Korea, one of their only exports, aside from counterfeit bills, is weapons and weapons technology. That's what they deal with. The bazaar is open, as far as they're concerned," McCormack said.