A 'litmus test' for a looming recession could come next quarter, says an economist who's been predicting a downturn for 18 months

• Veteran economist David Rosenberg is maintaining his bearish call on the US economy.
• He told CNBC in an interview the fourth quarter of this year would be the "litmus test" for his call.
• He added a recession typically starts two years after a rate hike cycle begins.

Veteran economist David Rosenberg has been calling a recession for the last 18 months, and he isn't letting the current resilience in the US economy change his mind.

"It hasn't materialized, dot dot dot, yet," Rosenberg told CNBC on Wednesday, in response to his bearish call.

But he maintains a recession is looming.