International Atomic Energy Agency chief Mohamed ElBaradei told reporters, the Associated Press reported, "We have not seen diversion of nuclear material for weapons purposes, but the picture is still hazy and not very clear."
ElBaradei arrived in Tehran Thursday -- a day after Iranian President Mahmoud Ahmadinejad announced his country had for the first time successfully enriched uranium -- hoping to convince nuclear officials to halt uranium enrichment and return to two-year-old negotiations with the European Union and United States.
The United Nations, prompted by the European Union and United States, has demanded Iran suspend its nuclear program. Western countries fear Tehran, accused of sponsoring terrorists, could use the uranium to fuel nuclear weapons. Iran insists it has the right to enrich uranium to generate power for peaceful purposes.
"We won't hold talks with anyone about the right of the Iranian nation (to enrich uranium)," the country's official news agency quoted Ahmadinejad as saying Thursday, the AP reported.
China, Russia, the United States, Britain and France -- the five permanent members of the U.N. Security Council -- met in New York to discuss Iran's announcement.
The council has given Iran until April 28 to suspend its program or face further action. That action could include imposing sanctions on the country, though China and Russia have opposed the notion.
"We are obviously following this very carefully and we want to see what the outcome of the discussions between ElBaradei and the Iranian government is, and when we get information on that we'll consider what to do next," U.S. Ambassador to the United Nations John Bolton told reporters after the meeting.
The dispute between Iran and the international community has raised questions about how long it would take Iranian nuclear scientists to gather the materials and know-how to build a weapon if that were the country's aim.
Responding to that question Thursday, U.S. intelligence officials said Iran remains years away.
"There is still a very significant amount of time that needs to be worked through by Iranians to get to where they want to go," said Kenneth Brill, head of the Bush administration's newly created National Counterproliferation Center, according to the AP.
Also Thursday, China, which has called on Iran to stop uranium enrichment, but which disagrees with the United States over how best to achieve a deal with Iran, said it is sending an envoy to Iran and Russia to discuss the impasse.