The United Nations says UN-Arab League envoy Kofi Annan will engage Iran in efforts to restore calm in Syria.

Annan will brief Tehran after Saturday's international meeting in Geneva and "will also ensure their [Tehran's] continued engagement," UN spokesman Martin Nesirky said on Wednesday, AFP reported.

Annan "has been clear about the need for Iran to be part of the solution and so has the secretary general," Nesirky noted.

The Geneva meeting will gather foreign ministers of all five permanent members of the UN Security Council and several regional countries.

Annan says the Geneva meeting aims to secure full implementation of his six-point peace plan.

Despite objections from United States, UN Secretary General Ban Ki-moon, Annan himself, and Russian Foreign Minister Sergei Lavrov have called for Tehran’s attendance.

Annan’s initiative came into force in April but it has failed to end the unrest, but UN reports reveal violence has only intensified ever since.

Iran has voiced full support for the UN-brokered peace plan, repeatedly ruled out a military intervention in Syria, and denounced the US-spearheaded sending of military assistance to terrorist groups in the country.