DAMASCUS, June 3 (Xinhua) -- Syrian President Bashar al-Assad said Thursday the cause of the Palestinians is the essence of conflicts in the region and the world, the Syrian Arab News Agency (SANA) reported. At a meeting with U.S. Congress members Brian Bard and Lenkin Davis, al-Assad indicated that Israel responded to all of the peace opportunities by waging wars on the serious efforts exerted to achieve progress on this process, particularly the Turkish mediation. Relationship between Turkey and Israel has been severely deteriorated after Israeli navy attacked an aid flotilla in its way to Gaza on Monday, causing nine killed on board, including eight Turkish citizens and one Turk with American nationality. The two sides discussed the relationship between Damascus and Washington as Bard and Davis expressed the desire to boost this relationship due to Syria's role in achieving peace in the region, SANA said. Last month, U.S. President Barack Obama extended sanctions against Syria for a year, saying it supports terrorist groups in the region and pursues weapons of mass destruction. In the last few weeks, however, Damascus witnessed several visits by U.S. legislators including Democratic Senator John Kerry who arrived on May 22 to discuss with the Syrian leader relationship between the two countries.