A spokesman also said the government was not worried about being referred to the UN for possible sanctions.
"Although we think referral of Iran's case to the Security Council would be unlawful and politically motivated, if one day they refer Iran's case ... we won't be worried in the least," said Foreign Ministry spokesman Hamid Reza Asefi.
Britain, Germany and France, heading nuclear negotiations with Iran for the European Union, have called an emergency meeting of the International Atomic Energy Agency's (IAEA) board of governors on Tuesday to discuss Iran's case.
The EU trio say they will recommend referring Iran to the Security Council if it goes ahead with plans to break UN seals and resume work at the Isfahan uranium conversion plant.
Iran, which on Saturday rejected an EU package of economic and political incentives designed to persuade it to halt nuclear fuel work for good, says it will restart the Isfahan plant as soon as IAEA surveillance equipment is in place.
"The European proposal has no value," state television quoted Foreign Minister Kamal Kharrazi as saying.
"We will insist on our rights and have decided to resume Isfahan activities as the first step of our measures. This does not mean we will stop negotiations with Europe," he added.
Iran says it has a right to
Asefi, speaking at a weekly news conference, said IAEA technicians would be at the Isfahan plant on Monday to install additional cameras.
He said the 35-page EU proposal, which contained an offer of help with developing a civilian nuclear programme, was rejected because it did not recognise Iran's right to enrich uranium.
EU offer rejected
Iran's official reply will be delivered to the EU on Monday.
"I suggest that the Europeans avoid the language of threat," Asefi said. "The only way is to encourage Iran and respect its
"The only way is to encourage Iran and respect its rights"
Hamid Reza Asefi,
Iran Foreign Ministry spokesman
Some newspapers declared the EU proposal worthless.
"Their proposal is an empty box in beautiful wrapping," Jomhuri-ye Eslami daily said. "If Iran agrees to it, it will be deprived of the nuclear fuel cycle forever and it would be an everlasting scandal for Iran."
Iran says its nuclear programme is solely designed to produce much-needed electricity and is not, as Washington insists, a cover for making atomic bombs.
It says that as a signatory of the nuclear Non-Proliferation Treaty (NPT) it has the right to produce its own fuel for nuclear reactors, a process that can also be used to make bomb-grade material.
The Kayhan newspaper, which has long called for Iran to kick out UN inspectors and withdraw from the NPT, on Sunday argued that Iran was in fact not a member of the treaty since parliament had not ratified it.
Iran's new president Mahmoud Ahmadinejad, at his swearing-in ceremony on Saturday, said Iran would not be intimidated by threats from the West.
A religious conservative loyal to the ideals of the 1979 Islamic revolution, Ahmadinejad is expected to adopt a tougher position on the two-year-old nuclear negotiations with the EU, analysts and diplomats say.