* Lavrov may try convince Riyadh to involve Iran in talks
* Moscow eyes bigger regional role in Middle East
By Gabriela Baczynska
MOSCOW, Nov 14 (Reuters) - Russia is expected to urge Saudi Arabia to allow its regional rival Iran to join moves to end the conflict in Syria in a rare high-level meeting on Wednesday between the world's top two oil producers, diplomatic sources said.
Foreign Minister Sergei Lavrov is hoping to raise Moscow's profile in a region where its influence is at risk after blocking three U.N. resolutions meant to put pressure on Syrian President Bashar al-Assad to end the bloodshed.
The Syrian uprising, which has cost 38,000 lives in 20 months, has further strained traditionally uneasy ties between Russia and Saudi Arabia, a key ally of the United States.
The trip to Riyadh is Lavrov's second Middle East visit in less than two weeks. Last week in Cairo he embraced an Egyptian-backed drive to bring together four regional powers to seek a solution to the Syrian crisis.
Saudi Arabia, which supports the rebels fighting Assad, has skipped two ministerial meetings of the group, which includes Egypt and Turkey - also critics of Assad - and Iran, Syria's closest regional ally.
Lavrov's efforts to persuade Saudi Arabia to back the inclusion of Iran in peace efforts are seen as unlikely to succeed.
"Lavrov has supported Egypt's regional quartet initiative, but the problem there is that the Saudis don't want to take part in a format that includes Iran. So he will be trying to convince them to change their minds," said Fyodor Lukyanov, editor of the magazine Russia in Global Affairs.
Russia is under pressure to do more to end the violence in Syria and risks being sidelined. Moscow denies Western accusations it is shielding Assad, saying it is driven by the need to prevent meddling and let Syrians decide their fate.
"On Syria, Russia has cornered itself," a European diplomat in Moscow said. "It has been promoting Iran's right to participate ... so Lavrov may raise that with Riyadh, though he is not going to achieve much."
A Middle East source also said there was little chance of any breakthrough at the talks in Riyadh.
Russia has insisted that any new U.N. resolution should be based on a June 30 agreement reached by international powers in Geneva that envisaged a transitional government in Syria.
The United States said the deal signalled to Assad that he must leave power, while Russia disagreed. Neither Iran nor Saudi Arabia were represented at the talks, with Washington, London and Paris accusing Tehran of helping Assad crush the uprising.
Back then, Russia was saying both should have been invited.
"The Russians would like to broker some sort of arrangement on Syria, a managed transition that will preserve their equities and those of their clients in Syria," said Nikolas Gvosdev, professor at the U.S. Naval War College.
The Russian Foreign Ministry has said little about the visit beyond announcing that Lavrov will meet Saudi officials as well as attending a meeting between Russia and the six-nation Gulf Cooperation Council on issues including Syria.
"There is no way in the world Saudi Arabia would sit down to talks with Iran - and even if it did, it would not be Russia convincing them to do that. So this trip really is just about Russia trying to be present in the Middle East," another diplomatic source in Moscow said.
"Russia is trying to put itself in the position of an intermediary between various forces there. You see the same mechanism in them talking to various Syrian opposition groups and Assad."
Chilly ties between Moscow and Riyadh date to the Soviet war in Afghanistan in the 1980s, when Saudi Arabia backed anti-Russian militants. Russia has been concerned by the presence of Saudi and other Arab militants fighting in the post-Soviet wars in Chechnya and the Islamist insurgency they spawned.
A diplomatic source in Moscow said Lavrov's visit may be a "damage control" attempt after Riyadh condemned as hostile remarks by a Russian official who in July expressed "great concern" over human rights in Saudi Arabia.