Gholamreza Agha-zadeh, head of Iran's Atomic Energy Organization, says that Tehran has not changed its nuclear plans and will continue to install more centrifuges.
Agha-zadeh made the remarks following Wednesday's launch of a test run for its first nuclear power plant near the southern Iranian port city of Bushehr.
"We have 6000 centrifuges operating today in the Natanz nuclear plant and we will increase this number next year. Our plan is to install all 50,000 centrifuge machines within next five years. From a certain time in the near future, we will enter the phase of installing new-generation machines."
He said that the United States should face reality and accept living with "a nuclear Iran."
The 1,000-megawatt nuclear power plant, originally scheduled for operation in 2007, is expected to be put in use by the end of this year after repeated delays.
The United States has accused Iran of developing nuclear weapons under the cover of its peaceful use of nuclear energy.