* Iran's Rouhani in Ankara to discuss Syria, trade
* Says Tehran-Ankara ties essential for stability
* Turkey to repeat demand for lower Iran gas price
* Iran wants Turkey to drop legal case over gas price
By Parisa Hafezi and Tulay Karadeniz
ANKARA, June 9 (Reuters) - President Hassan Rouhani, whose country's relations with Turkey have been strained by the Syrian civil war, said in Ankara on Monday Iran would make tackling extremism, sectarian conflicts and terrorism its chief objective.
Pragmatist Rouhani, whose foreign policy of "prudence and moderation" has eased Tehran's international isolation since his landslide election last year, arrived in Turkey on Monday for a two-day visit, a first by an Iranian president since 2008.
Iran and Turkey have found themselves on opposite sides of the political fence over a Syrian civil war that has killed 160,000 people and sent hundreds of thousands of refugees streaming into Turkey.
Shi'ite Iran has backed Syrian President Bashar al-Assad since the start of the uprising while Turkey has been one of his fiercest critics, supporting his opponents and giving refuge to rebel fighters. Ankara has described Assad's forces as using terrorist methods while Tehran has used similar language in criticising opposition groups.
"Instabilities exist in our region ... Iran and Turkey are determined to increase their cooperation to establsh stability in the region," Rouhani said after talks with President Abdullah Gul in Ankara
"The Fight against violence, extremism, sectarian conflicts and terrorism is Irans major objective," he added.
Gul said that Syria was discussed during his meeting with Rouhani, without giving any details. It was unclear whether the two countries were approaching any concrete steps to help scale down a conflict that holds perils for both.
Despite deep divisions between Ankara and Tehran over Syria, the potential of an Iranian market of 76 million people with some of the world's biggest oil and gas reserves is a magnet for Turkish companies.
Turkey depends on imports for almost all of its natural gas needs and is keen to increase oil and gas imports from Tehran in anticipation of sanctions against Iran's huge energy sector being dismantled.
GAS PRICE DISPUTE
A senior Turkish official told Reuters that Ankara will repeat its demand for a discount on the price of natural gas from Iran, which Ankara says is too expensive compared with other suppliers like Russia and Azerbaijan.
Under a contract signed in 1996, Turkey imports 10 billion cubic metres per year of gas from Iran. The contract became active in 2001.
Turkey's state-owned Petroleum Pipeline Corporation (BOTAS) applied to an international court of arbitration in 2012 for a ruling on Iran's gas pricing. The case is still pending.
"The Iranian side demanded dropping of the legal case and it was discussed during the talks," said a Turkish official on condition of anonymity.
Iran has so far dismissed Turkish demands it drop the price of gas under the current agreement.
Rouhani's visit to Turkey takes place as Iranian, U.S. and European Union officials hold talks about Tehran's disputed nuclear programme in Geneva in an effort to break a logjam in wider negotiations over Tehran's nuclear program.
Nuclear talks between Iran and six major powers in Vienna last month to reach a final deal ran into difficulties, with each side accusing the other of having unrealistic demands in negotiations.
A preliminary deal was penned in Geneva in November between Iran and six major powers, under which Iran accepted to halt some sensitive nuclear activities in exchange for partial easing of sanctions. It went into effect in January 20.
(Additional reporting by Orhan Coskun in Ankara, Michelle Moghtader in Dubai, Writing by Parisa Hafezi)