The future of Afghanistan had been the original focus of the summit in Trieste, but Iran's post-election violence has shifted the attention.

As a neighbour of Afghanistan, Iran had been invited to attend the summit along with other bordering countries.

But Iran's foreign minister has said he has "no plans to travel to Italy".

The BBC's Duncan Kennedy in Rome says the summit would have offered a rare chance for G8 leaders to meet senior Iranian diplomats to discuss the country's controversial nuclear programme.

But protests by opponents of President Mahmoud Ahmadinejad - who say he has unjustly claimed victory in the recent elections - have changed the agenda of the talks, says our correspondent.

Tens of thousands of people have taken to the streets in protest and at least 17 people have died in clashes with riot police.

Tehran says the protests are illegal and the election result is accurate - a stance which is expected to be condemned by some G8 members.

Italian Foreign Minister Franco Frattini earlier met Iran's charge d'affaires in Rome to discuss Foreign Minster Manouchehr Mottaki's absence from the summit, the AFP news agency quoted a ministry statement as saying.

Rome said it hoped that "in the future Iran will be able to engage in a profitable way in the process of regional stabilisation in Afghanistan".