The Pentagon Chief has arrived in Riyadh for his first official visit to Saudi Arabia since taking the post this summer.
"US Secretary of Defence Mark Esper arrived in Riyadh today to meet with key Saudi and US leadership to discuss mutual regional concerns", Pentagon spokeswoman Rebecca Rebarich said.
A day earlier Mark Esper had arrived in Kabul to meet with Afghan President Ashraf Ghani for another unannounced visit. Esper said at a press conference in Kabul that Washington was considering leaving a small contingent of US troops in Syria to secure oil fields and continue fighting terrorists.
The US has increased its presence in the Persian Gulf over the past several months, as tensions between Tehran and Washington have escalated. The United States deployed up to 3,000 troops, Patriot missile batteries, a Terminal High Altitude Area Defence (THAAD) system, and other assets to help strengthen Saudi Arabia's defences.
A series of attacks on tankers in the Gulf of Oman and Hormuz Strait, as well as a drone attack against oil facilities of Saudi Arabia last month, have worsened the situation, with Washington and its allies placing the blame for the attacks on Iran. Tehran has refuted all accusations.
Most recently, Iran reported two attacks with an interval of around 30 minutes on its own tanker some 60 miles from the Saudi port city of Jeddah. Reportedly a terrorist attack, the case is currently under investigation by Tehran and Riyadh.
*Daesh (also known as ISIS/ISIL/IS) is a terrorist group banned in Russia