The United States blacklisted a number of additional companies and people under sanctions aimed at Iran's nuclear program, officials said in a statement on Thursday.
Treasury and State Department officials said the move shows the recent agreement reached in Geneva over Iran "does not, and will not, interfere with our continued efforts to expose and disrupt those supporting Iran's nuclear program or seeking to evade our sanctions."
The move comes as some U.S. lawmakers push to impose further sanctions on Iran. But the Obama Administration has so far persuaded them to hold off, saying further action could harm ongoing talks with Iran.
It is the first such enforcement action since the United States and other nations reached a first step agreement with Iran in Geneva last month.
"We will continue relentlessly to enforce our sanctions, even as we explore the possibility of a long-term, comprehensive resolution of our concerns with Iran's nuclear program," said David Cohen, the Treasury Department's under secretary for terrorism and financial intelligence.
Cohen continued with "...the United States is working to make clear to international oil companies and other firms that sanctions on Iran remain in place and they should not be reaching out to the Islamic republic. We are very actively dissuading international oil companies and others who think that now may be a time to test the waters in Iran."
Cohen said Treasury Secretary Jack Lew has met recently with more than 100 bank chief executives and other business leaders to make it clear that sanctions on Iran remain in place.
Administration officials said Thursday's action targeted entities that are involved in the proliferation of materials for weapons of mass destruction and have tried to evade the current sanctions.
Officials said Thursday's targets include companies and individuals engaged in transactions on behalf of other companies that the United States has also previously designated under the sanctions. They include Mid Oil Asia, Singa Tankers, Siqiriya Maritime, Ferland Company Limited and Vitaly Sokolenko.
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.
Treasury's Cohen, along with State Department Under Secretary for Political Affairs Wendy Sherman, are set to appear before a Senate hearing about the Geneva deal later on Thursday.