Oil flirted with bear-market territory as Saudi Arabia insisted OPEC will avert a global supply glut after international trade brinkmanship triggered the steepest monthly slump this year. Futures gained as much as 2.1% in New York on Monday before surrendering those gains and extending the decline to a fourth session. Saudi Energy Minister Khalid Al-Falih said Monday that recent volatility is “unwarranted” and predicted allied crude producers will continue efforts to avoid an oversupply for the rest of 2019. Al-Falih’s assurances weren’t enough to calm traders worried that simmering trade d...