Iran has announced it has started installing a new generation of machines for enriching uranium at its main facility making nuclear fuel.
Iranian media quoted Fereydun Abbasi-Davani, head of Iran's Atomic Energy Organization, as saying on February 13 that new centrifuges began to be installed at the Natanz site last month.
He said the new centrifuges will only be used to produce low-level enriched uranium.
Monitors say the new machines could enable Iran to enrich uranium much faster than is currently possible.
The Iranian announcement comes as a delegation from the United Nations' nuclear watchdog held talks in Tehran on the possibility of new inspections.
Ali Asghar Soltanieh, Iran's envoy to the International Atomic Energy Agency (IAEA), said the two sides agreed on some points at the meeting on February 13. He did not elaborate on the exact agreements.
IAEA officials had been expected to push for access to documents and nuclear officials that would allow the agency to restart a stalled investigation into suspected nuclear weapons research by Tehran.
The IAEA was in particular expected to push for inspecting the Parchin military base, where nuclear weapons parts have allegedly been tested.
The visit comes ahead of the nuclear talks scheduled for February 26 in Kazakhstan between Iran and six world powers after a gap of eight months.
Ahead of those talks, EU foreign-policy chief Catherine Ashton has told a UN Security Council meeting she hopes Iran will show flexibility at the talks, so that substantial progress can be made to address international concerns about Iran's nuclear program.
Ashton has been coordinating the talks on behalf of the United States, Russia, China, Britain, France, and Germany.
Iran has refused to suspend its uranium enrichment program, which Western states suspect is aimed at producing nuclear weapons.
Iran says its nuclear program is entirely peaceful.
Based on reporting by Reuters, AP, and dpa