RIYADH, Sept. 18 (Xinhua) -- Escalating tensions across the Middle East are increasingly weighing on Saudi Arabia, one of the world's largest oil exporters. As the ongoing U.S.-Iran conflict continues to disrupt shipping through the Strait of Hormuz, growing hostilities between Yemen's Houthi group and Saudi Arabia are also threatening Riyadh's oil export routes through the Red Sea, putting mounting pressure on S