Iran said on Saturday it would decide in coming days whether to resume uranium enrichment activities after a tough UN resolution sharply rebuked Tehran for not co-operating fully with nuclear inspectors.
Enrichment, a process of purifying uranium for nuclear power plants, can also be used to make atomic weapons. A resumption of enrichment would fuel US accusations that Iran wants a nuclear weapons capability and could provoke a major crisis.
Tehran, which says its nuclear programme is merely geared to generating electricity, was angered by a meeting of the International Atomic Energy Agency (IAEA) which passed a resolution on Friday criticising its co-operation and transparency.
"Iran will review its decision regarding suspension and we will announce our decision in the coming days," Hassan Rohani, secretary-general of Iran's Supreme National Security Council, told a news conference.
An Iranian reaction to the IAEA resolution had been expected. Tehran retaliated following the last IAEA board meeting in March, which also criticised its co-operation, by suspending inspection visits for nearly a month.
Iran agreed to suspend enrichment last October, saying it was a voluntary and temporary measure aimed at restoring international confidence following revelations that it had kept secret sensitive nuclear research for nearly two decades.
Rohani stressed, however, that Iran would probably not resume pumping uranium hexafluoride gas into centrifuges, which spin at high speed to produce enriched uranium.
"I should underline that our decision might not be resuming enrichment itself, it might be other activities such as building parts... Probably we will continue not to inject gas into centrifuges for a while," he added.
Britain, France and Germany, the three countries which brokered the enrichment suspension last October, have expressed annoyance that Iran continues to make centrifuge parts at private workshops. Friday's IAEA resolution again urged Iran to desist from this work.
A spokeswoman for the IAEA declined comment on Rohani's statements.
US envoy to the IAEA Kenneth Brill said on Friday a resumption of enrichment activities "would be another demonstration of (Iran's) true colours".
"They are determined to have an enrichment programme and one that goes well beyond the needs of a power programme, that underscores their desire to pursue military purposes for their nuclear programme," he told reporters.
While "deploring" what it said was Iran's poor co-operation with the UN nuclear watchdog, the IAEA resolution did not set any new deadlines for Iran or contain a trigger mechanism for its case to be sent to the UN Security Council for possible sanctions, as Washington wanted.
Rohani said Iran was keen to resolve all outstanding questions about its nuclear activities.
"Iran is ready to co-operate and work with the agency...and will continue to implement the Additional Protocol," allowing snap inspections of nuclear sites, he said.
He dismissed accusations Iran had an undisclosed site in north Tehran, as Washington alleges from satellite photographs.
"I am saying openly that Iran, apart from the sites it has openly declared...has no other places for enriching uranium," he said.