In Vienna Monday, Mohamed ElBaradei said IAEA inspectors have seen a slowing in the installation of centrifuges that enrich uranium at Iran's Natanz nuclear facility.

IAEA officials visit Tehran this week.

In other news, The Washington Post newspaper says the IAEA is concerned about construction seen in recent satellite photographs of a mountainside next to the Natanz facility.

The report quotes an IAEA spokeswoman as saying the agency has "received clarifications" from Iran about the construction. It says the spokeswoman did not elaborate.

The newspaper says governments, intelligence agencies and nuclear experts are studying the satellite images to try to figure out if Iran is placing key parts of the nuclear facility underground to thwart any military strike against it.

Iran has defied U.N. demands to halt uranium enrichment, a process that can be used to build nuclear weapons.

The United States and its allies accuse Iran of trying to develop nuclear weapons. Iran says the program is for peaceful purposes. - VOA News