Iranian President Mahmoud Ahmadinejad has warned the European Union against imposing sanctions, saying his country would cause it to "regret" the move.
Mr Ahmadinejad said that anyone who adopted hostile measures "should know that Iran will react swiftly".
EU foreign ministers are expected on Monday to formally approve restrictions on Iran's energy sector, to impede the development of its nuclear programme.
The decision comes a month after the US strengthened its own sanctions on Iran.
The US and its allies accuse Tehran of seeking to develop nuclear weapons. Iran insists its nuclear programme is solely for peaceful purposes.
The Security Council imposed a fourth set of UN sanctions on Iran in June over its continued refusal to halt the enrichment of uranium.
The EU and US decided shortly after to put in place additional restrictions.
The EU sanctions will reportedly include a ban on the sale of equipment, technology and services to the vital Iranian energy sector, which is intended to inhibit its refining, exploration and production activities.
The bloc will also ban the sale to Iran of dual-use goods that could be used for conventional weapons and further monitor banks with connections to Iran.
On Sunday, President Ahmadinejad warned that any countries or institutions supporting Washington's "scheme" would be considered "hostile" to Iran, and that it would "respond strongly to any threat".
"We do not welcome any tension or a new resolution. We seek logic and friendship," he was quoted as saying by Iran's state-owned Press TV channel.
"I should tell you that anyone who adopts a measure against the Iranian nation... should know that Iran will react swiftly," he added. "Experience shows that such a reaction by the Iranian nation will cause you to regret it."
Meanwhile, Turkish Foreign Minister Ahmet Davutoglu has said Iran has expressed willingness to hold talks on its nuclear programme with the European Union in September, after the Islamic holy month of Ramadan.
"The Iranian foreign minister confirmed once again they are ready to start negotiations," he said after talks with Manouchehr Mottaki and his Brazilian counterpart, Celso Amorim in Istanbul.
Mr Davutoglu also said Tehran would send a letter on Monday to the International Atomic Energy Agency (IAEA) asking to start separate "technical negotiations" on implementing an agreement with Turkey and Brazil to exchange Iran's low-enriched uranium for more highly-enriched fuel rods.