PARIS (Reuters) - President Emmanuel Macron s initiative in bringing Lebanon s Saad al-Hariri to Paris puts France at the center of a power struggle between Sunni Saudi Arabia and Shi ite Iran and will test a policy of neutrality that critics doubt can be sustained.  While the move eased regional tensions that spiked after the prime minister s resignation on Nov. 4, it also exposed the difficulty of Macron s stated position of taking no sides in the Middle East.  Macron has put his neck out on Lebanon,  said a European diplomat who didn t want to be named talking about an ally s policies.  It s a bit like his moment of truth.  Hariri, a Saudi ally, arrived in France on Saturday days after announcing his resignation while in Riyadh, accusing Iran and its Lebanese ally Hezbollah of creating strife. Many Lebanese believe the Saudis made him quit. President Michel Aoun has not accepted the resignation and Hariri is expected to return to Beirut on Wednesday, when Lebanon celebrates the end of France s colonial mandate in 1943. Macron s maneuver, which came after a visit to Saudi Crown Prince Mohammed bin Salman and a flurry of calls, appears to have taken the foreign ministry by surprise, an example of his penchant for bypassing state organs to show he s in charge, much like former leader Nicolas Sarkozy.  So far it s a symbolic victory for French diplomacy that has enabled a reduction in tensions,  said Stephane Malsagne, a lecturer at Sciences Po University in Paris, adding it was a  risky gamble  that could antagonize all sides.  Macron set out his foreign policy objectives for the region in his first speech to the diplomatic corps in August, saying he wanted France to maintain a balanced position.  We will achieve our goal of fighting terrorism only if we do not make the mistake that would impose a choice between Shi ites and Sunnis, and in a sense, force us to lock ourselves in one camp,  he said at the time. Some French diplomats say Macron will find it difficult to appease everyone, however.  Lebanon maintains a delicate sectarian balance after Sunnis, Shi ites, Christians and Druze fought a civil war between 1975 and 1990, with factions often backed by regional rivals. Hariri is Sunni Muslim and President Aoun, a political ally of Hezbollah, is Christian. Hariri s government, a power-sharing coalition formed last year, includes Shi ite Hezbollah.  This mediation is an introduction for a new French political role in Lebanon ... (and) a French attempt to find a foothold starting from Lebanon into the region,  said a senior Lebanese official, speaking on condition of anonymity.  But in the shadow of big players (U.S., Russia, Iran, Saudi Arabia) in the region, the French will face difficulties.   Since Hariri announced his resignation, Saudi Arabia has accused Lebanon of declaring war on it, citing Hezbollah s role in fighting in other Arab countries.     France has a long history of commercial, political and social links with Iran that even saw Ayatollah Ruhollah Khomenei exiled near Paris in 1979, but it was arguably the most demanding of the six powers negotiating the 2015 nuclear accord. Under Presidents Sarkozy and Francois Hollande, who aligned themselves with Qatar and Saudi Arabia, respectively, there was a hawkish shift toward Tehran. Since the deal, Paris has been quick to restore trade ties, with planemaker Airbus, oil major Total and automobile manufacturers Peugeot and Renault all signing deals. That rapprochement annoyed Riyadh, which has been moving closer to the United States under President Donald Trump.  We had to reassure the Saudis ... and rebalance things. Prince Salman has gone into overdrive and that s dangerous for  everyone so he needs some love from us,  said one French diplomat, who asked not to be identified.  Tehran is now chafing in turn over France s warming Saudi ties and what appears to be a good relationship with Israeli Prime Minister Benjamin Netanyahu, who is due in Paris on Dec. 10 for the second time since Macron took office in May. Recent rhetoric has reflected the tensions. At a news conference on Friday, Macron said Iran should clarify what is going on with its ballistic missile program which  seems to be uncontrolled . That followed a news conference in Riyadh on Thursday at which Foreign Minister Jean-Yves Le Drian denounced Tehran s  hegemonic temptations . On Saturday Ali Akbar Velayati, a senior adviser to Iran s supreme leader, told Macron to stay out of its affairs. Le Drian has pushed back a planned visit to Tehran and talk that Macron may visit next year has become more muted.   Speaking to all sides is noble, but this policy in the region will come tumbling down if Le Drian and Macron do not go to Tehran. Our credibility depends on it,  said a second French diplomat. Some hardline politicians in Iran have criticized President Hassan Rouhani for trying to strengthen ties with Paris, saying Europeans will not endanger their interests in the face of U.S. pressure. A senior Iranian official said Macron s policy of  balance  ultimately just offered mixed signals.  He talks about curbing Iran s defensive missile work and criticizes Iran s regional policy and then he wants to build closer ties?  the official said.   France should clearly announce which side Paris is taking.... we like to expand our relations but Paris sends mixed signals and cannot be trusted.  