G8 leaders also said they were "seriously concerned" about recent events in Iran, saying media restrictions and the detention of foreign nationals were "unacceptable".
But Al Jazeera's Alan Fisher, reporting from the G8 summit, said the US and Britain were keen to avoid action that could further deteriorate relations with Iran.
Relations between Iran and the West have been severely strained in recent times. Many western powers accuse Tehran of covertly developing nuclear weapons, a charge that Iran denies. Tehran insists its nuclear programme is aimed at generating electricity for civilian use.
During the second day of talks in L'Aquila, G8 leaders and five emerging economic powers agreed to complete stalled Doha trade talks in 2010, in an effort to head off protectionist policies in the wake of the global recession.
A draft joint declaration signed by the groups said: "We reaffirm our commitment to maintain and promote open markets and reject all protectionist measures in trade and investment".
The Doha global trade talks, which were initially to conclude in 2004, have been beset by difficulties and delayed for months. A deal would cut goods tariffs and subsidies around the world.
The G8, G5, Egypt, South Korea and Australia also set a ministerial meeting before a September meeting of the G20 in the United States.
The G8 is also seeking to reach consensus on Thursday on new climate change targets with emerging market nations.
On the first day of talks on Wednesday, the group agreed to try to limit global warming to two degrees Celsius compared with pre-industrial levels, and pledged to cut their greenhouse gas emissions by between 50 and 80 per cent by 2050.
"I hope we can agree the two degrees Celsius target with all the countries around the table today," Gordon Brown, Britain's prime minister, said shortly before the second day of talks began.
But environmentalists reacted negatively to the G8 plans, with delegates failing to set short-term goals.
Kim Carstensen, from the World Wild Fund for Nature, said: "If they don't outline a path to reach the announced goal, the two degree statement will just join a long list of broken promises."
Thursday's talks will be opened up to include the five fastest developing market economies of Brazil, China, India, Mexico and South Africa.
Group of Five
The "Group of Five" will discuss climate change, development aid, global economic growth and international trade with their G8 counterparts.
|The so-called Group of Five includes India, Mexico, Brazil, South Africa and China [AFP]
But progress over climate change talks could be hampered by the absence of Hu Jintao, the Chinese president, who withdrew from talks to deal with ethnic clashes his country.
Indian negotiators have said developing countries want to see rich nations provide financing to help them cope with more floods, heatwaves, storms and rising sea levels, caused by global warming.
But Silvio Berlusconi, Italy's prime minister, said everyone should help combat the problem.
"It would not be productive if European countries, Japan, the United States and Canada accepted cuts that are economically damaging while more than five billion people in other countries carried on as before," he said.
Before the talks, the leaders had said that climate change, the economy and Africa would be the priorities at the L'Aquila gathering.
Charity workers have expressed disappointment at what they see as broken promises from leaders, after Italy announced a 56 per cent cut in its aid budget this year.
A heavy security presence is surrounding the talks, with about 15,000 police officers and soldiers deployed in L'Aquila and Rome.
Officials are hoping to prevent a recurrence of the violence seen during the country's last G8 meeting in 2001.
Berlusconi moved the G8 venue from Sardinia to L'Aquila, where more than 250 people died in an earthquake which struck the town in April. The premier believes hosting the summit in L'Aquila will help to rebuild the area.