(CNN) -- Iran has 5,000 "running centrifuges" in its main nuclear site at Natanz, according to Iranian news reports quoting a top official.
The United States and other Western nations have been pressing Iran to suspend uranium enrichment, believing Tehran wants to develop nuclear weapons. Iran insists it wants to use the technology to produce electricity.
Reza Aqazadeh, head of the Atomic Energy Organization of Iran made the remarks while speaking to reporters on the sidelines of his tour of the Exclusive Exhibition on Nuclear Industry Achievements in Tehran.
"Suspension of nuclear enrichment is meaningless and it is not found in our vocabulary," Aqazadeh told reporters, according to Iranian news agencies.
Spinning centrifuges are used to separate atoms in uranium ore to produce uranium concentrated enough for use in a nuclear power plant or a nuclear weapon's fission chain reaction.
In April, President Mahmoud Ahmadinejad promised to install 6,000 more centrifuges over the coming year. In August, Iran's deputy foreign minister said the nation had about 4,000.
Diplomats from several countries said that while the 5,000 number is accurate, there is a difference between centrifuges that are working and ones that are spinning perfectly.
In Iran's centrifuges the spinning has not yet been perfected but is improving, they said. Most estimates say Iran is about a year away from developing a nuclear weapon.
David Albright -- president of the Institute for Science and International Security, a Washington group dedicated to informing the public about science policy issues -- said the figure is credible and that "Iran is marching onward in developing its nuclear weapons capability."
CNN's Elise Labott contributed to this report