MOSCOW—Armenian President Armen Sarkissian tendered his resignation on Sunday, saying he believes the country’s constitution does not give him sufficient powers to influence events. Sarkissian, president since 2018, was in a standoff with Prime Minister Nikol Pashinyan last year over a number of issues, including the dismissal of the head of the armed forces. The role of prime minister is seen as more powerful than that of president. “I have been thinking for a long time, I have decided to resign from the post of the President of the Republic after working actively for about four years,” Sarkissian said in a statement published on the president’s official website. “The question may arise as to why the President failed to influence the political events that led us to the current national crisis. The reason is obvious again—the lack of appropriate tools …—the Constitution. The roots of some of our potential problems …