Wall Street bear Peter Boockvar warns that 2019's market rally is flawed, and a major setback will slam stocks.

His chief reasons include sluggish global growth, the earnings slowdown and a fuzzy economics picture.

"I would be fading this rally thinking that it's more of a bear market bounce rather than this is the beginning of a bull market," the Bleakley Advisory Group chief investment officer said Tuesday on CNBC's "Futures Now." "The higher the market goes [and] the lower earnings estimates go, the more expensive the market is getting."

Boockvar was on the bear circuit in 2018, too. Last summer, the CNBC contributor told "Futures Now" the U.S. market would get swept up in a wave of corrections. By October, his forecast began unfolding.

And now, he's telling clients that a pullback retesting the December lows is a real threat.

"If you look at the actual underlying economic fundamentals, they're deteriorating, particularly overseas," he said. "With respect to corporate earnings, we're seeing a decline in earnings expectations for this year."

According to Boockvar, it's not unreasonable to worry about the earnings slowdown developing into a full-blown earnings recession.

"It's a risk because it's happening in the context of stalled monetary tightening," said Boockvar.

Boockvar, whose firm has $4.5 billion in assets under management, also sees the Federal Reserve's decision to put its interest rate hike policy on hold as a bearish signal.

"At some point, the market is going to ask itself, 'Why is the Fed done raising interest rates?' It's not because they've achieved their objective of getting around 3 percent [GDP growth]," he added. "It's because the data, particularly overseas, caused them to take a step back."