Iran will continue nuclear negotiations with world powers, even after pulling out of expert-level talks to protest against the US targeting companies it says evaded current sanctions, the country's foreign minister has said.
Mr Zarif wrote: "We will continue Geneva talks. We will show proper, calculated, purposeful and smart reaction toward any improper and unconstructive action."
He also wrote: "Talks and reaching a conclusion is a difficult job and it will definitely have ups and downs. We had predicted this from the first day."
The West fears Iran's nuclear program could allow it to build nuclear weapons. Iran says its programme is for peaceful purposes.
Other companies involved directly in the proliferation of material useful for weapons of mass destruction were also blacklisted from the US market.
American citizens are banned from any transactions with the listed individuals and firms.
The US move comes as 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.
The West fears Iran's nuclear programme could allow it to build nuclear weapons. Iran says its programme is for peaceful purposes like power generation and medical treatment.
Mr Zarif and the government of moderate President Hassan Rouhani also face criticism at home by hard-liners over the Geneva deal - and Thursday's sanctions. The foreign minister also addressed them in his Facebook post.
"Some friends who were not happy with the Geneva action plan have announced its early death, which is an expression of their wish rather than the reality," Mr Zarif wrote. "We will answer all the criticism and ambiguities in appropriate time."