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U.S. stocks came under renewed pressure Tuesday, but volatility could still provide buying opportunities in the American equity market, strategist Michael Zinn told CNBC.

"Every time you see market dislocation, what you have to look at is whether it's crossed important thresholds and established a down trend," said Zinn, UBS senior vice president of wealth management.

At this point, it appears that fear and emotion are roiling markets, and investors should not succumb, Zinn said on CNBC's "Squawk Box."

"You have to have a discipline that establishes when you take a different tack, but I don't think we've reached it yet, particularly not if you're in the U.S., because we've got an economy that's picking up steam and not showing any signs of overheating."

U.S. markets were rattled after data showed China's manufacturing activity slowed significantly last month.

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China's official manufacturing purchasing managers' index (PMI) dipped to 49.7 in August from 50 in July. The final Caixin/Markit read on PMI slipped to 47.3 in August, the lowest reading since March 2009 and down from 47.8 in July.

Japan's Nikkei sank 3.8 percent, while China's Shanghai composite fell nearly 1.3 percent. Major European averages were all down more around 2 percent, as were U.S. stock futures.

While U.S. fundamentals look sound, correlations with weakening economies run together during times of stress and volatility, Zinn said. That creates a case for buying U.S. equities and remaining patient through September, a notoriously bad month for stocks, he added.

"You may have a chance at better valuations here in the U.S. in both growth and value sectors because of what we're seeing, because really, the U.S. may end up benefiting from what we're seeing overseas," he said.

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Also on "Squawk Box," Russell Investments strategist Stephen Wood said the chance that U.S. stocks could fall into bear market territory is "non-trivial," but his firm is not ready to make that forecast.

"This might be a time to shake out some marginal positions and reposition over the next six to 12 months," he said.

—CNBC's Ansuya Harjani contributed to this story.