Gholam Reza Aghazadeh, head of the Atomic Energy Organisation of Iran, said on Tuesday the country would "voluntarily" suspend its centrifuge work starting 9 April.
Iran "is interested as quickly as possible to bring this case to a close," he said.
Muhammad al-Baradai, director-general of the International Atomic Energy Agency, welcomed the announcement and said a new team of inspectors would travel to Tehran on 12 April to verify that all uranium enrichment activities had stopped.
Al-Baradai arrived in Tehran late on Monday to meet with Iran's president and top Iranian officials in an effort to press the regime for greater openness with its suspect nuclear programmes.
Al-Baradai said the IAEA and the Iranian government agreed on accelerating the cooperation to resolve outstanding issues.
Aghazadeh said he expected Iran's nuclear dossier would be closed by June, at the next meeting of the IAEA's board of governors.
But Tuesday's announcement countered Iran's claim on 29 March that it had stopped building centrifuges for uranium enrichment.
Aghazadeh: Iran wants to bring
case to a close
Al-Baradai's trip to Iran was meant to address such indications of continued nuclear cover-ups and signs that even previously reluctant US allies were moving closer to the United States' view that Tehran should be penalised.
Al-Baradai said that he hoped that the US and Iran could sit together to clear the American "scepticism" against Iran.
Iran insists its nuclear programme is peaceful and geared only toward producing electricity.
The United States and other nations contend it masks a covert effort to build a nuclear weapon, and an IAEA resolution last month censured Iran for hiding suspicious activities. Al-Baradai was to return to Vienna on Wednesday.
Earlier, al-Baradai told reporters in Frankfurt before flying to Iran for the meeting: "Iran has been actively cooperating, but I sense some slowdown in the process."
"It is in the interests of Iran to show from now until June maximum transparency, maximum accelerated cooperation," he said.
The IAEA's board of governors meets in June when it will issue a fresh report on the status of inspections in Iran.
"It is in the interests of Iran to show from now until June maximum transparency, maximum accelerated cooperation"
A group of Western diplomats who follow the IAEA have said recent intelligence has prompted suspicion Iran has not stopped enriching uranium, but has moved enrichment activities to smaller sites out of view from the United Nations.
"We haven't seen any indication, nor have we got any information that they have been moving," said al-Baradai.
Iran promised Britain, France and Germany last October it would suspend uranium enrichment and accept snap atomic checks.
If enriched to a low level, uranium can be used to fuel nuclear power stations. But if enriched further, to weapons grade, it can be used in warheads.