The UN nuclear watchdog has not made much progress in resolving outstanding issues over Iran's nuclear programme, the agency's chief says.
Iran insists it has a right to enrich uranium
Mohamed ElBaradei was speaking at the opening of a meeting of International Atomic Energy Agency (IAEA) governors.
He welcomed a package of incentives put forward by six major powers to persuade Tehran to stop uranium enrichment.
Iran has not given its response to the offer, but has warned the IAEA not to jeopardise efforts to resolve the row.
"We need a restrained, cool and constructive debate," Ali Asghar Soltanieh, Iran's ambassador to the IAEA, told Reuters news agency ahead of the meeting in Vienna.
Iran insists its programme is entirely peaceful and is designed to meet its energy needs only.
In his speech, IAEA director general Mohamed ElBaradei said the organisation had "not made much progress in resolving outstanding verification issues".
"I would continue to urge Iran to provide the co-operation needed to resolve these issues," he added.
He welcomed "the recent efforts" by the five permanent members of the UN Security Council and Germany "that aim to reach a comprehensive agreement".
"I remain convinced that the way forward lies through dialogue and mutual accommodation among all concerned parties," Mr ElBaradei went on.
The 35-nation IAEA board of governors is due to debate Tehran's nuclear programme later in the week.
Western diplomats are expected to encourage as many board members as possible to support the package of incentives offered to Tehran in exchange for suspending uranium enrichment.
But no action is likely to be taken unless Iran responds to the offer, the BBC's Bethany Bell in Vienna says.
The package was drawn up by Britain, France, Germany, the US, Russia and China.
Its contents have not been made public, but are said to include the lifting of restrictions on the use of US technology and support for Iranian membership of the World Trade Organization.
Iran allowed to buy spare parts for civilian aircraft made by US manufacturers
Restrictions lifted on the use of US technology in agriculture
Provision of light water nuclear reactors and enriched fuel
Support for Iranian membership of World Trade Organization
From Western diplomatic sources
The offer was presented to the Iranian authorities earlier this month by the EU foreign policy chief Javier Solana, who has since said he expected a response from Tehran this week.
Western diplomats have signalled satisfaction with Iran's initial response to the plan - which may allow Tehran to enrich uranium at some point in the future.
The US envoy to the IAEA, Gregory Schulte, said: "The next decision needs to be taken not in Vienna but in Tehran."
He said IAEA members hoped that decision would be to suspend all enrichment-related and reprocessing work "and to take advantage of the enormous diplomatic opportunity that lays in front of the Islamic republic".
Earlier, Iran again said it would not negotiate over its right to enrich uranium - a process which can be used for atomic power plants or for nuclear weapons.
"We have obtained this technology, it is our obvious right and we do not negotiate over our obvious nuclear rights," government spokesman Gholamhossein Elham said.