The United States on Tuesday imposed further sanctions on Iran over its controversial nuclear program by identifying 21 entities believed to be owned or controlled by the Iranian government.

As the latest move of unilateral sanctions on Iran, the Obama administration identified the entities, including two Belarus- based banks, two Germany-based investment firms, and mining and engineering companies in Japan, Germany, Luxembourg, Italy and Iran.

"By identifying these entities, including banks, investment companies and technology firms, U.S. persons and others are better able to identify Iranian Government entities and protect themselves against the risks posed by such entities," said a statement by the Treasury Department.

"As its isolation from the international financial and commercial systems increases, the Government of Iran will continue efforts to evade sanctions, including using government-owned entities around the world that are not easily identifiable as Iranian to facilitate transactions in support of their illicit activities," said Under Secretary for Terrorism and Financial Intelligence Stuart Levey.

"Today's identifications will mitigate the risk that such entities pose to legitimate transactions," said Levey.

The United States, Israel and their Western allies worry that Tehran may obtain the uranium fuel needed for developing nuclear weapons. That claim was rejected by the Iranian government, which insists its nuclear program is for peaceful purpose only.

The Obama administration has been trying the "dual-track" strategy, a combination of diplomatic mediation and economic sanctions, to bring the international community together to make Iranian leaders realize the "importance of changing their actions and decisions concerning their nuclear program."

After pushing the UN Security Council to adopt Resolution 1929 for imposing more sanctions on Iran in June, the Obama administration has been trying to make more countries take unilateral sanctions against Tehran.