The announcement marks the second time the United States has designated sanctions evaders since reaching an interim deal with Tehran in November.
Washington says it will continue to enforce existing sanctions until there is a more comprehensive deal to prevent Iran from developing nuclear weapons.
"We strongly believe that sustaining sanctions pressure will be critical," a senior US Treasury official told journalists by telephone.
Under that agreement between Iran and six major powers, including the United States, Tehran agreed to curb sensitive nuclear activities in exchange for some limited sanctions relief, including the transfer back to Iran of $4.2 billion in oil funds held abroad.
Top administration officials insisted to lawmakers in Senate testimony this week that Washington would continue to enforce its existing sanctions on Iran.
Concerned about trade delegations, such as a visit to Tehran this week by 100 business leaders from France's biggest firms, some members of Congress want the sanctions regime expanded despite the administration's objections.
Iran says that its nuclear program is peaceful and denies Western and Israeli accusations that it is seeking the means and expertise to assemble a nuclear warhead. It also maintains that it is Israel's reputed atomic arsenal that threatens peace.
The actions taken on Thursday prohibit companies and individuals from carrying out financial transactions under US jurisdiction.
Businesses and individuals targeted
The US Treasury said the targeted businesses and individuals operated in Turkey, Spain, Germany, Georgia, Afghanistan, Iran, Liechtenstein and the United Arab Emirates.
Some were helping Iran evade sanctions on oil exports as well as its efforts to acquire prohibited nuclear and military technologies, according to the Treasury. They included a Spanish firm that the United States said was helping Iran's nuclear industry.
The United States targeted a Turkish citizen for allegedly helping Iran try to acquire and reverse engineer a "weapons-capable" speedboat. Washington also accused German firm Deutsche Forfait of helping "facilitate oil deals" with Iran.
Other violators named were associated with Iran-sponsored activities in Syria and Afghanistan, Treasury said in a statement.
Some US lawmakers are pushing for new sanctions laws to be imposed on the Islamic state, but the Obama administration has campaigned to hold off on new measures to give diplomatic efforts to settle the nuclear dispute a chance.
Senator Robert Menendez, chairman of the Senate Foreign Relations Committee, made a 45-minute speech on Thursday arguing that the measure should move ahead with a sanctions bill that is stalled in Congress.
"I believe in the lessons of history that tell us Iran cannot be trusted to live up to its word without external pressure," the New Jersey Democrat said on the Senate floor.
The Treasury last imposed Iran sanctions in December, shortly after the interim deal was struck, blacklisting several companies and individuals for supporting Iran's nuclear program.
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