Government spokesman Gholam Hossein Elham said research activities would resume on Monday under the supervision of the International Atomic Energy Agency, the United Nations nuclear watchdog.
Iran's Foreign Ministry spokesman Hamid Reza Asefi confirmed the research work will go ahead.
"We will remove the seals and we have announced that we are ready to start research from tomorrow," he told a news conference.
He said Iran has the right to do so, and refused to say what kind of research was planned or which sites are involved.
The European Union has warned that such a move is likely to endanger efforts to restart talks on ending the crisis between the West and Tehran over the latter's nuclear ambitions.
The United States has also said that resuming research into the fuel cycle may lead it to refer Iran to the UN Security Council for action.
Washington has accused Iran of seeking to build nuclear weapons, a charge Tehran denies, saying its nuclear program is merely for peaceful civilian use.
Tehran has sought to highlight that its research into the nuclear fuel cycle is separate from actually producing uranium, which can be used as fuel in civil reactors or as the core of an atomic bomb.
Talks between Iran and the EU broke down last August after Iran resumed uranium conversion activity, after halting the work in 2004.
More nuclear talks due
The announcement comes after talks between Russia and Iran on a proposed compromise to end the row broke off unresolved on Sunday, however are set to resume in a month.
The two countries are trying to reach a solution on proposals to transfer Iran's uranium enrichment activities to Russian soil.
"Negotiations to reach a final conclusion are going to be continued on February 16 in Moscow," said Hossein Entezami, spokesman for the National Security Council which is in charge of the nuclear file.
"Negotiations ended on Sunday after three rounds of talks, which resulted in some understandings," he was quoted in Monday's press as saying.
Russia wants Iran to conduct uranium enrichment on its soil to allay Western fears that the technology could allow Iran to produce a nuclear bomb, a proposal backed by both the EU and US in principle.
The board of governors of the IAEA is due to meet in March to discuss whether to hand the Iran issue to the UN Security Council, which could impose sanctions on the country.