Muhammad al-Baradai was speaking on Monday as the board of governors of his International Atomic Energy Agency (IAEA) met one day after Iran's nuclear planners scored a major victory with a key uranium fuel supply deal with Russia.
"We are moving forward, we are making progress," al-Baradai said while urging Iran to be more helpful to IAEA nuclear inspectors.
"I would continue to ask Iran to be more proactive and provide us with information that can accelerate our work."
Iran, Opec's second largest oil producer, says its nuclear intentions are limited to peaceful generation of electricity.
Washington says the programme is a front to build a bomb.
Al-Baradai said the agency had been able to verify Tehran's suspension of activities connected with uranium enrichment, a process of purifying uranium for use as fuel for nuclear power plants or, when very highly enriched, in weapons.
Iran says its nuclear programme
is for peaceful purposes
This, he said, "is a good thing".
The IAEA's 35-member board was not expected to pass any resolutions this week that would condemn Iran or refer it to the UN Security Council for possible sanctions, diplomats said.
The European Union has demanded Iran make the suspension permanent if it is to get access to economic and political incentives including telecommunications and aircraft deals and possible membership of the World Trade Organisation.
Washington says Tehran must accept the EU offer or be referred to the Security Council for possible sanctions.