Israeli Prime Minister Benjamin Netanyahu said he was unimpressed by a report from the UN's International Atomic Energy Agency on Thursday that Iran had frozen its nuclear activities.
Iran's archenemy Israel takes a hard line on international pressures for Tehran to rein in its controversial nuclear programme and has not ruled out military action against it.
"I am not impressed by the report published this evening," Netanyahu was quoted by his office as saying.
"Iran does not need to expand its programme because it already possesses the necessary infrastructure for building a nuclear weapon."
The IAEA said that, in the past three months, only four new centrifuges had been installed at Iran's Natanz plant, compared with 1,861 in the previous period.
At the Fordo facility, which also enriches uranium -- which can be used for a nuclear weapon if highly purified -- no new centrifuges were put into operation, the report seen by AFP showed.
The report added that Iran has also not begun operating any new-generation IR-2M centrifuges and that "no... major components" had been installed at a reactor being built at Arak.
The faster IR-2M centrifuges are of concern to world powers because, in theory, they shorten the time Iran would need to produce enough weapons-grade uranium for a nuclear bomb.
And the so-called IR-40 reactor at Arak is a worry because it could provide Iran with plutonium, an alternative to uranium for a nuclear weapon.
Iran insists its nuclear programme is peaceful.
The IAEA report was released ahead of a new round of talks between Iran and world powers in Geneva next week after three days of gruelling talks last week ended with no agreement.
The international community wants Iran to freeze the most sensitive parts of its nuclear programme -- not just to stop expanding it.
This includes the enrichment of uranium to fissile purities of 20 percent, close to weapons-grade, and a halt to construction at Arak.
In return Iran wants UN and Western sanctions that have been hammering the Islamic republic's economy to be eased soon, and its "right" to enrich uranium recognised.
Israel, the region's sole if undeclared nuclear power, views a nuclear Iran as an existential threat and has said it will not be "bound" by any world deal with Tehran, refusing to rule out the threat of military action to halt it.