Piling up pressure on Iran, the leaders of the world's eight most powerful economies have asked it to swiftly address all outstanding issues related to its nuclear programme and vowed to ensure that crude markets are 'fully and timely' supplied despite oil embargo on Tehran.

In its 'Camp David Declaration', the G-8 grouping also supported Kofi Annan's settlement plan for Syria and cautioned North Korea against further provocations, besides pledging to take steps to mitigate economic impact of Afghan transition and stressing that Greece, which is battling a crippling debt crisis, should remain in the Eurozone.

As Iran faced sanctions, the G-8 leaders said increasing disruptions in the global oil supplies 'pose a substantial risk' to the world economy.

"Looking ahead to the likelihood of further disruptions in oil sales and the expected increased demand over the coming months, we are monitoring the situation closely and stand ready to call upon the International Energy Agency to take appropriate action to ensure that the market is fully and timely supplied," the joint declaration said.

At the end of a series of brain-storming sessions that began with a dinner in this US presidential retreat on Friday night, the G-8 expressed 'grave concern' over Iran's nuclear programme and urged Tehran to meet the requirements of International Atomic Energy Agency's (IAEA) Board of Governors in this regard.

"We also call on Iran to address without delay all outstanding issues related to its nuclear programme, including questions concerning possible military dimensions," the declaration said adding that the G-8 countries desire a peaceful and negotiated solution to concerns over Iran's nuclear programme, and therefore remain committed to a dual-track approach.

The G-8 asked Iran to seize the opportunity that began in Istanbul, and sustain it in Baghdad by engaging in detailed discussions about near-term, concrete steps that can, through a step-by-step approach based on reciprocity, lead towards a comprehensive negotiated solution which restores international confidence that its nuclear programme is exclusively peaceful.

Earlier, the US President Barack Obama said that the G-8 leaders are united on their approach to Iran, noting that all these powerful countries agree on Tehran's right to a peaceful use of nuclear energy but nuclear weapon is unacceptable to them. "We are unified on our approach to Iran."

"We are hopeful about the discussions that will be taking (place) in Baghdad (on Wednesday), but all of us are firmly committed to continuing with the approach of sanctions and pressure, in combination with diplomatic discussions," Obama told the biggest gathering of foreign leaders at Camp David.

On Syria, the G-8, appalled by the loss of life, humanitarian crisis and serious and widespread human rights abuses in the country, backed Annan's plan to resolve the ongoing crisis in the country.

"The Syrian government and all parties must immediately and fully adhere to commitments to implement the six-point plan of UN and Arab League Joint Special Envoy (JSE) Kofi Annan, including immediately ceasing all violence so as to enable a Syrian-led, inclusive political transition leading to a democratic, plural political system," the G-8 leaders said.

On North Korea, the leaders asked the country to refrain from any provocative actions like missile launch and comply with its international obligations.

"We continue to have deep concerns about provocative actions of the Democratic People's Republic of Korea (DPRK) that threatens regional stability."

Reaffirming their commitment to a sovereign, peaceful and stable Afghanistan, the G-8 leaders said they were committed to taking steps to mitigate the economic impact of the transition as the US-led international forces prepare to withdraw from the war-torn country by 2014.