WASHINGTON (Reuters) - Underscoring growing concerns about Iran, the Bush administration has decided to impose new sanctions on Chinese, Armenian and Moldovan companies accused of aiding Tehran's alleged weapons of mass destruction programmes, a senior U.S. official said on Wednesday.

He told Reuters the U.S. Congress would be formally notified soon of the decision, which is being taken under the Iran Nonproliferation Act of 2000.

The official, who spoke on condition of anonymity did not disclose the names or numbers of the companies affected nor the exact nature of their activities. But he said both the number of sanctions imposed and the number of companies and individuals penalised are "going up".

The entities to be sanctioned are engaged in activities prohibited by multilateral export control lists, such as the Missile Technology Control Regime, which seeks to curb the transfer of longer-range missiles, and the Australia Group, a 33-nation nonproliferation regime that seeks to prevent the spread of chemical and biological weapons.

The official said companies and individuals in Moldova and Armenia to be sanctioned may be a "front" for Russian entities, given those countries' status as former Soviet

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U.S. President George W. Bush addresses students during a his visit to a school in Milwaukee, Wisconsin, on May 8. REUTERS/Kevin Lamarque