RIYADH/DUBAI - Russian President Vladimir Putin said before his first visit to Saudi Arabia in more than a decade that Moscow could play a key role in easing regional tensions given its good ties with Sunni Muslim Gulf Arab states and Shi'ite Iran.Putin also told Arab broadcasters in an interview aired on Sunday he had no reliable information about who was behind last month's attack on Saudi oil facilities.Yemen's Houthi movement responsibility for the Sept. 14 attacks, but Riyadh and Washington blamed Tehran.Tehran denied responsibility for the drone and missile strikes that rattled global oil markets and exposed major gaps in Saudi air defenses, prompting the United States to send around 3,000 more troops to the kingdom."It is wrong to determine who is guilty before it is known reliably and clearly who is behind this act," Putin said, adding that he had agreed to help investigate the attack."Imagine, we don't know. The next day, I asked the head of the foreign intelligence service and the defense minister. 'No, we don't know.'" he said according to an Arabic-language transcript provided by Saudi-owned Al Arabiya television.The Russian president is due to arrive in Saudi Arabia on Monday and then heads to the United Arab Emirates on Tuesday.Tensions in the Gulf region have risen to new highs since May 2018, when the Trump administration withdrew from a 2015 international nuclear accord with Tehran that put limits on its nuclear program in exchange for the easing of sanctions.As Trump reinstated U.S. sanctions, increasing pressure on Iran's economy, there have been a series of attacks in Saudi Arabia and in Gulf waters that Washington and close allies have blamed on Iran, which denies responsibility.Putin said such attacks only strengthened cooperation between oil producers inside and outside OPEC, an alliance known as OPEC+, and that Russia would work with its partners to reduce attempts to destabilize markets.He said he had "very friendly personal relations" with Crown Prince Mohammed bin Salman, the de facto Saudi ruler who has won praise for plans to wean the economy off oil and open up society but faced an international outcry over a devastating war in Yemen and human rights abuses, including last year's murder of journalist Jamal Khashoggi.IRAN DEAL, SYRIAAsked if Moscow supported new a return to negotiations with Iran to limit its missile program as Trump has called for or enforcing the nuclear deal first, Putin said the two issues should be dealt with separately."Most likely it (the missiles) can and should be discussed ... The missile program is one thing and the nuclear program is another thing," he said. "Of course, this is necessary, but there is no need to merge one with the other..."On Syria, where Russia and Iran have been key allies of President Bashar al-Assad in an 8-1/2-year civil war, Putin said any new constitution that is drawn up should guarantee the rights of all ethnic and religions groups.A congress convened by Russia last year tasked the United Nations envoy for Syria with forming a committee to draft a new constitution, after many rounds of talks to end the war failed.U.N. officials say forming a constitutional committee is key to political reforms and new elections meant to unify Syria and end a war which has killed hundreds of thousands and displaced about half of the pre-war 22 million population.Putin said Syrians "interact positively" with Russian military police and military stationed in the country and that most military police in Syria were Muslims drawn from Russia's north Caucasus region.Turkey launched an assault last week against Kurdish forces in border areas of northern Syria, saying it seeks to set up a "safe zone" to resettle Syrian refugees but raising international alarm over the possibility of Islamic State militants escaping from prisons.