"We are pursuing the negotiations seriously and of course we will give a well-considered, purposeful, smart and proper reaction to any inappropriate and unconstructive move," Foreign Minister Mohammad Javad Zarif wrote on his Facebook page.
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This was despite the Americans having made "inappropriate moves to which we gave the appropriate response by considering all aspects of the issue".
"The negotiations and achieving a result are a difficult task and will definitely have a lot of ups and downs. We have predicted that from the very beginning."
The United States blacklisted a dozen overseas companies and individuals on Thursday for evading its sanctions imposed on Iran to halt what the West sees as its bid to build a nuclear bomb.
Senior US officials argued the move was taken under an existing sanctions regime which had forced Tehran to negotiations that led to an interim deal under which it agreed last month to freeze parts of its nuclear program.
The measures, which angered Iran and prompted its negotiating team to withdraw from the talks in Vienna, have drawn strong criticism in the Islamic Republic.
But Zarif vowed to answer at the right time domestic critics who were using his "necessary silence" to voice their displeasure at the nuclear deal reached with the six world powers in Geneva on November 24.
"Some friends who were not happy with the Geneva joint action program have already announced its premature death, which is more the expression of their desire rather than the truth," he said on Facebook.
"The negotiating team has a more important responsibility... and is ready to remain silent against unjust and unfair accusations for the sake of national interests, but will answer to all the criticism and ambiguity at the right time."
Under the interim deal reached in Geneva, Iran agreed to freeze parts of its suspect nuclear program in return for some relief from Western sanctions as it negotiates a comprehensive accord to allay suspicions that it seeks a weapons capability.
The United States also agreed to refrain from slapping new sanctions on Iran.
Top administration officials argued that Thursday's blacklisting was carried out within the framework of the existing sanctions regime and did not constitute new measures.
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