Tehran said on Monday it will keep talking with world powers on its disputed nuclear programme despite a US move to blacklist Iranian companies for evading sanctions.
"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.
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."
He later told CBS television in the United States: "The process has been derailed, the process has not died." Zaris also told the network's Face the Nation programme that Iran is committed to the Geneva accord, adding however: "It takes two to tango."
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 programme.
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.
Since last day, conservative newspapers have condemned the "violation of the Geneva deal" by the American administration.
Some hardline students from the Islamist militia (Basij) have written an open letter to Zarif urging him to "defend the dignity" of Iran "by giving a firm response." In the letter, published today by Iranian newspapers, they also backed the decision of the negotiating team to quit the Vienna talks.