Iranian negotiators in Vienna called off nuclear talks late Thursday with world powers, citing a need for “consultations” with Tehran.

“The Iranian negotiators interrupted the talks with the P5+1 [Britain, China, France, Russia and the United States, plus Germany] for consultations in Tehran,” the Islamic Republic New Agency (IRNA) reported Friday.

AFP reported Friday that the decision to halt the talks came hours after Washington blacklisted a dozen overseas companies and individuals for evading US sanctions on Iran.

“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,” Treasury undersecretary for terrorism and financial intelligence David Cohen was quoted by AFP as saying.

Negotiators from both sides had been discussing implementation measures to the interim nuclear deal reached in the Swiss capital last month, in which Iran agreed to scale back parts of its controversial nuclear program in exchange for sanctions relief.

The six-month interim deal was meant to allow both sides to reach a more permanent, comprehensive agreement.

IRNA reported that the next round of talks would be held in Tehran on January 21, 2014.

On Thursday, the US government targeted more than two dozen companies and people for evading sanctions against Iran, an effort by the Obama administration to show it will enforce existing law even as it presses Congress to hold off on additional measures while world powers pursue a comprehensive nuclear deal with Tehran.

The action freezes the US assets of firms in Panama, Singapore, Ukraine and elsewhere for maintaining covert business with Iran’s national tanker company. Other companies involved directly in the proliferation of material useful for weapons of mass destruction also were blacklisted from the US market. American citizens are banned from any transactions with the listed individuals and firms.

The announcement by the Treasury and State departments came as the administration was furiously lobbying lawmakers to refrain from any new package of sanctions on Iran after last month’s agreement. As part of the deal, the US agreed to no new nuclear-related financial penalties against Tehran for six months, and Iran’s foreign minister has warned that any such action could kill the diplomatic effort.

Still, many Republicans and Democrats in Congress have called for even tougher measures to raise the pressure further on the Islamic republic, despite the administration’s pleas for patience.

Also Thursday, at a US Senate Committee on Banking, Housing and Urban Affairs, top American nuclear negotiator Wendy Sherman sought to assure members that the interim deal was effective, and that sanctions relief through the deal will be minimal.

But Sherman used conditional language that appeared to indicate a reluctance to commit that the ultimate level of sanctions relief, offered to Iran under the deal for partially freezing its rogue nuclear program, would indeed be held to the previously stated $6-7 billion.

Recent reports in Israeli media have suggested that ultimately, the total sanctions relief offered in the agreement will be closer to $20 billion, and have also asserted that various “under the table” concessions were made to Iran in Geneva.

Rebecca Shimoni Stoil contributed to this report.