The U.S. Treasury on Thursday imposed sanctions on two North Korean bankers and a trading company, citing their links to Pyongyang's development of weapons of mass destruction.

It marks a swift step to follow through on the U.N. Security Council resolution on North Korea adopted two days earlier for its December rocket launch.

The move is also seen as a show of the Obama administration's firm stance not to bow to North Korea threats of another nuclear test and more long-range rocket launches.

"By continuing to expose these entities, and the individuals who assist them, we degrade North Korea's ability to use the international financial system for its illicit purposes," Under Secretary for Terrorism and Financial Intelligence David S. Cohen said.

Designated were Ra Kyong-Su, the Tanchon Commercial Bank (TCB) representative to Beijing, and Kim Kwang-Il, the TCB deputy representative to Beijing.

TCB serves as the financial arm of Korea's Mining Development Trading Corp. (KOMID), already under United Nations sanctions.

KOMID is known as the secretive communist nation's main arms dealer and exporter of goods and equipment related to ballistic missiles and conventional weapons.

The Treasury also added Hong Kong-based Leader International Trading Limited to its blacklist for facilitating the shipment of machinery and equipment to customers on behalf of KOMID. 

The department's announcement came hours after the White House accused North Korea of taking a "needlessly provocative" step with a threat to conduct another nuclear test.

"North Korea's statement is needlessly provocative," White House press secretary Jay Carney said in a press conference.

A nuclear test by North Korea would be a significant violation of U.N. Security Council resolutions that will only lead to further isolation of the communist nation, he added.

Carney took note of the council's unanimous adoption of Resolution 2087 calling for U.N. members to expand sanctions on Pyongyang.

"These tightened sanctions will help impede the growth of weapons of mass destruction programs in North Korea, and the United States will be taking additional steps in that regard," said Carney.

Carney's comments came in response to North Korea's strongly worded statement of its intention to launch more long-range rockets and carry out what would be its third nuclear test.

The North, angry about the new U.N. Security Council resolution, said the upcoming actions will "target" the U.S. (Yonhap News)