"In the last four months we have made quite good progress in clarifying the outstanding issues," Mohamed ElBaradei, director of the International Atomic Energy Agency (IAEA), said in a statement accompanying a new report on Iran's nuclear activities.
"However, that is not in my view sufficient," he said, highlighting Iran's failure so far to address reports about possible links between uranium enrichment, missile warhead design work and high-explosives tests.
In this respect, ElBaradei urged Tehran to implement "as actively as possible, as fast as possible" the IAEA's Additional Protocol, which allows snap inspections of Iranian nuclear facilities.
"We need to have that authority as a matter of law," he said.
Meanwhile, Iranian chief nuclear negotiator Saeed Jalili hailed the IAEA report as yet another proof that Iran's nuclear research was peaceful.
"This report showed that our activities are peaceful," Jalili told a news conference in Tehran shortly after the IAEA report was released in Vienna.
"I congratulate the Iranian people on this success and victory, which was a result of their persistence in defending the country's inalienable rights [for peaceful nuclear research]," he said.
Jalili said Iran would continue cooperation with the IAEA and strictly observe the provisions of the Non-Proliferation Treaty.
The diplomatic standoff between Iran and the West began almost six years ago over suspicions that Tehran was developing a secret weapons program. Tehran has always maintained it needs nuclear technology for peaceful purposes. Since then, two rounds of sanctions have been imposed - in December 2006 and March 2007.
The five permanent UN Security Council members and Germany agreed at talks in Berlin on January 22 on a draft for a third sanctions resolution against Iran calling for travel bans, asset freezes and vigilance on all banks in the Islamic Republic.
The new draft resolution was officially introduced by France and Britain in the UN Security Council earlier on Friday, and council members are expected to vote on the resolution at some point next week.
The outcome of the vote will largely depend on the assessment of the new IAEA report.
Iran Six negotiators will meet on February 25 in Washington to discuss further steps in dealing with Iran's nuclear issue.