Iranian President Hassan Rouhani said that tensions in the Middle East region were caused by the "US economic war" against Iran."If we witness some tensions in the region today, their root cause lies in the U.S. economic war against Iranian nation," Xinhua quoted Rouhani as saying during a joint press conference with the visiting Japan's Prime Minister Shinzo Abe on Wednesday."Whenever this (economic) war is stopped, we will witness very positive developments in the region and in the world," he said.Rouhani expressed gratitude for Abe's efforts for regional stability and security.He hoped that Abe's trip to Iran would serve as "a prelude to development of mutual ties as well as regional good."Abe arrived in Iran's capital Tehran on Wednesday with a plan to help ease tensions between Iran and the US.During his two-day visit, he is also scheduled to meet with the Iranian Supreme Leader Ayatollah Ali Khamenei on Thursday.