The Obama administration announced Thursday that it was cracking down on a number of companies and individuals U.S. officials say used deceptive practices to help Iran further its nuclear program.

The enforcement measures come amid lawmaker skepticism of a diplomatic deal between the U.S. and Iran that would see Tehran freeze some aspects of its nuclear program in exchange for some sanctions relief. The White House managed to stave off efforts in Congress to pass further sanctions to heighten pressure on Iran and officials have sought to reassure lawmakers they will stay tough on Tehran and enforce those sanctions remaining in place.

The Treasury and State Department said they were targeting businesses who evaded international sanctions designed to cripple Iran’s nuclear ambitions. The actions would freeze the assets of those individuals and companies determined to have violated the sanctions and bar U.S. entities from doing business with them.

U.S. officials said the six-month nuclear agreement between the U.S. and Iran won’t interfere with the administration’s continued efforts to “expose and disrupt those supporting Iran's nuclear program or seeking to evade our sanctions.”

“These sanctions have isolated Iran from the international financial system, imposed enormous pressure on the Iranian economy, and motivated the Iranian leadership to make the first meaningful concessions on its nuclear program in over a decade,” said Treasury Under Secretary for Terrorism and Financial Intelligence David S. Cohen.

“Today’s actions should be a stark reminder to businesses, banks and brokers everywhere that 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,” he added.

Senate Banking Chairman Tim Johnson, D-S.D., said this week that his committee would not pursue new sanctions against Iran at this time.

Johnson said Secretary of State John Kerry had made a strong case for a “pause in Congressional action on new sanctions, so I am inclined to support their request and hold off on committee action for now.”

The Banking committee is the leading panel charged with overseeing sanctions legislation in the Senate. That panel, along with the Foreign Affairs committees in the House and Senate have been debating for months whether to impose new restrictions on doing business with Iran to try to force Tehran to roll back its nuclear program.

Several key lawmakers have pushed hard for a new round of sanctions to keep up pressure on Iran.

On Monday, Iranian Foreign Minister Javad Zarif warned that any new U.S. sanctions would sink the interim nuclear deal and reminded the international community that Washington promised not to impose new sanctions as part of that agreement.

Kerry testified at a hearing of the House Foreign Affairs Committee Tuesday, and Wendy Sherman, the State Department's lead U.S. negotiator with Iran, along with Cohen, will testify before the Senate Banking Committee Thursday.

A senior administration official told reporters that the Treasury and State Department actions announced Thursday should not come as a surprise because the Obama administration has been “explicit” that existing sanctions “would remain firmly in place and we will continue to rigorously enforce them.”

The official said that when President Obama announced the deal late November he stressed that pressure on Iran's economy would continue to mount during the initial six-month period.

The Treasury Department said more than a dozen companies and individuals have worked with Iran by using front companies in foreign countries to deceive foreign suppliers and support Tehran's “illicit proliferation and evasion activities.” The individuals and companies are located all over the world, U.S. officials said, from Singapore to the Philippines, the Ukraine, Cyprus and in Iran.

“These actions demonstrate our continued commitment to vigorously [punish] those who evade our sanctions… and to make sure that no one in the international business and banking communities misunderstands or underestimates our intent to vigorously enforce” existing sanctions, the official said.

“We haven't let up, we won't let up,” the official added.

Critics of the nuclear deal between the U.S. and Iran, including Israeli Prime Minister Benjamin Netanyahu, argue that the six-month deal erodes the sanctions regime the U.S. and international community have spent years building. Businesses will use the six-month period to flood into Iran and those deals -- and the economic growth they spur -- will be hard to reverse if the U.S. determines that Iran is not complying with the terms of the deal, they say.

Administration officials are pushing back against that argument, and Thursday's action is designed to show that the U.S. will remain vigilant against businesses that view any diplomatic detente as a chance to exploit business opportunities in Iran.

“There is no reason to believe that Iran is now open for business,” the administration official said. “It is still subject to the toughest sanctions… probably in history.”

The official warned international businesses that viewing the six-month interim period as a time to rush in to build business ties with Iran would be “both foolish as a business matter and dangerous as a legal matter.”

This story was published at 9:02 a.m. and has been updated.