* Current regional quartet undermined by Iran-Saudi tensions
* Erdogan offers options at meeting with Iran's Ahmadinejad
Turkish Prime Minister Tayyip Erdogan said on Tuesday he had suggested to Iranian President Mahmoud Ahmadinejad three-way talks including Egypt on the Syria crisis, given the apparent Saudi objection to Iranian involvement in a current quartet.
Egypt formed that group with Iran, Turkey and Saudi Arabia, but the latter stayed away from a meeting hosted by Cairo last month. Riyadh's no-show was seen by diplomats as a reaction to the presence of Shi'ite Muslim Iran, the major rival of the Sunni Muslim kingdom for regional power and influence.
Egyptian President Mohamed Mursi subsequently cancelled a meeting of the four regional powers on Sept. 26 because of the absence of Erdogan from the U.N. General Assembly, according to Cairo's presidential spokesman.
Speaking to reporters on his return to Ankara from Baku, where he held talks with Ahmadinejad at an Economic Cooperation Organisation summit, Erdogan offered various options for countries to get involved in future Syria talks.
"We proposed a three-way system here. This system could be a trio of Turkey-Egypt-Iran," the state-run Anatolian news agency reported Erdogan as saying. "A second system could by Turkey-Russia-Iran. A third system could be Turkey-Egypt-Saudi Arabia."
Turkey, Egypt and Saudi Arabia have publicly supported the Syrian rebels while Iran has been the staunchest regional ally of Syrian President Bashar al-Assad, complicating any consensual approach among the four to defusing Syria's civil war.
Tensions between Ankara, which has also sheltered Syrian rebels, and Damascus have been simmering of late after a shell fired by Syrian forces killed five civilians in a Turkish border town. Ankara has since retaliated repeatedly for further shelling from the Syrian side, an area of heavy fighting between Syrian government and rebel forces.
Ankara has banned all Syrian aircraft from its air space and carried out inspections of planes travelling to Syria to prevent military equipment being sent to government forces there.
Erdogan on Tuesday also voiced support for moves by Lakhdar Brahimi, the U.N.-Arab League mediator in the Syria conflict, to secure a ceasefire in Syria after 19 months of bloodshed.
"Brahimi has taken a step. Let's at least secure a ceasefire during Eid al-Adha," Erdogan said. The Islamic feast holiday begins around Oct. 25.
Diplomatic sources have told Reuters that Brahimi is attempting to persuade the Syrian government and rebels to accept a ceasefire and allow U.N. monitors into the country to oversee it.
Brahimi, who replaced Kofi Annan after the former U.N. secretary-general resigned in frustration in August, has been travelling around the Middle East trying to persuade key regional powers to accept his plan.
But diplomatic sources familiar with Brahimi's proposals said on condition of anonymity that neither the Assad government nor the fractious opposition had shown any interest in halting the conflict, which has killed an estimated 30,000 people.
Brahimi's plan is similar to one that Annan tried unsuccessfully to implement, U.N. diplomats said on Tuesday.