dubai saudi arabia king salman begin visit russia thursday invitation president vladimir putin saudi state news agency spa say gulf ruler first trip moscow since become king 2015. visit two countries plan set billion fund invest energy project part efforts two world big oil producers expand cooperation russian energy minister alexander novak say early monday spa say two leaders would discuss bilateral regional issue give detail saudi arabia big oil producer organization petroleum export countries russia help forge deal opec producers cut output 1.8 million barrel per day january lift crude price saudi king start russia visit thursday state news agency