The United States has targeted more than a dozen companies and individuals for evading international sanctions against Iran and for providing support for Tehran's nuclear program.
The U.S. Treasury and State Departments announced they are freezing assets and banning transactions of the entities they say are involved in proliferating material used for weapons of mass destruction and who are attempting to evade sanctions.
Officials said Thursday the new targets include shipping firms and individuals based in Singapore, the Philippines and Ukraine .
The U.S. also named five Iranian entities it said are directly engaged in actions contributing to Iran's ability to enrich uranium. Several other entities related to Iran's ballistic missile program were also targeted.
David Cohen, the Treasury Department's under secretary for terrorism and financial intelligence, said Thursday's action black-lists additional companies and people under previously-issued measures.
The move comes as some U.S. lawmakers push to impose new sanctions on Iran. But the Obama administration has so far persuaded them to hold off, saying such action could harm ongoing talks with Iran on limiting its nuclear program.
Cohen and State Department Under Secretary for Political Affairs Wendy Sherman told a congressional hearing Thursday that imposing new sanctions on Iran would likely result in Washington losing the support of its allies.
These include the other so-called P5+1 countries - Britain, China, France, Germany and Russia - who, along with the United States negotiated the interim deal on Iran's nuclear program and enforced existing sanctions that often run counter to their own economic interests.
Sherman said the Obama administration is correct in asking Congress to hold off on imposing additional punitive measures on Iran.
"If we indeed say, 'well we really didn't mean it, we're now going to impose additional sanctions that you all will have to live with around the world,' our partners are likely to say, 'well, wait a minute here. You're changing the rules. We agreed to harm our own economies in service to diplomacy and you're not giving diplomacy a chance.'"
Treasury's Cohen agreed, stressing his concern that the U.S. could lose support if its international partners conclude Washington is not interested in a diplomatic solution to the Iran nuclear issue.
Senator Tim Johnson, who chairs the U.S. Senate Banking Committee that oversees sanctions legislation, said he agrees with the Obama administration that any new measures could disrupt negotiations seeking to curb Iran's nuclear program.
Iran's foreign minister has also said a new sanctions law would kill the interim agreement reached in Geneva last month. In the interim agreement, Tehran agreed to limit uranium enrichment in return for an easing of international sanctions.