A dozen countries are to attend a hastily called meeting in Tehran on Thursday to discuss ways to end the violence in Syria, Iranian Foreign Minister Ali Akbar Salehi said, without saying who was coming.

"The consultative meeting on Syria will be held tomorrow in Tehran with 12 to 13 countries from Asia, Africa and Latin America" represented, Salehi said on Wednesday, the official news agency IRNA reported.

"Our main argument is an end to the violence and the holding of national dialogue in Syria. Iran's efforts are aimed at ending the violence in Syria as soon as possible," he said.

Iran is the key ally to the Syrian regime of President Bashar al-Assad.

US pressure excluded Iran from a previous diplomatic initiative led by former UN-Arab League envoy Kofi Annan to engage countries with influence in Syria in dialogue.

On Monday, Iran's foreign ministry announced it was calling the conference, and said nations having "a principled and realistic position on Syria" would take part.

Deputy Foreign Minister Hossein Amir Abdollahian said the meeting would be at the level of foreign ministers, according to IRNA, but the reported on Wednesday that some countries may be represented by ambassadors instead.

On Tuesday, an official in Lebanon told AFP the Lebanese foreign ministry had informed Iran it would not attend "because it has never participated in any international meetings on Syria, in line with its policy of restraint."

Likewise, a UN spokesman said former envoy Annan would not be sending a representative.

Annan announced last week that he was quitting as Syria envoy because of the lack of international support for his peace plan.

Iraq's foreign ministry said on Wednesday it was not yet sure whether Iraqi Foreign Minister Hoshyar Zebari would attend.

A top aide to Iran's supreme leader Ayatollah Ali Khamenei, Saeed Jalili, met Assad in Damascus on Tuesday to discuss the situation in Syria and the plight of 48 Iranians taken hostage on the weekend by rebels saying they were Revolutionary Guards on a "reconnaissance mission".

Jalili vowed that Iran will never allow Assad's regime to fall, calling it part of an anti-Israeli axis in the Middle East led by Tehran.

"Iran will never allow the resistance axis -- of which Syria is an essential pillar -- to break," Jalili said.

"What is happening in Syria is not an internal issue but a conflict between the axis of resistance on the one hand, and the regional and global enemies of this axis on the other," he added.

Iran accuses Turkey, Saudi Arabia and Qatar of arming the opposition in Syria, in collusion with the United States and Israel, to overthrow Assad.

US and Syrian opposition reports in turn accuse Iran of military supporting Damascus.