Brace for another Fed rate hike thanks to a 'problematic' surge in oil prices, billionaire investor Jeff Gundlach says

• Expect another rate increase by the Fed at its next meeting due to a "problematic" surge in oil prices, billionaire investor Jeff Gundlach said. 
• "I think the probability of rate hikes is higher than what I thought before this oil spike happened," Gundlach said. 
• Oil prices have climbed past $90 a barrel after Saudi Arabia and Russia slashed production. 

Investors should brace for another interest-rate increase by the Federal Reserve, with the recent surge in oil prices likely to rekindle inflation pressures, billionaire investor Jeff Gundlach said.