Prepare for deeper selloff if this happens: Cashin

Cashin: 10-year thermometer for global anxiety

If yields on benchmark 10-year Treasury bonds dip below 2.6 percent, then the ongoing rout on Wall Street could turn into something deeper, veteran trader Art Cashin told CNBC on Tuesday.

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"If you get down below 2.6—or 2.58 for sure—people might say maybe there's a lot more here than we know about and I think I want to be cautious," Cashin said on "Squawk on the Street."

Yields on 10-year Treasury bonds dipped sharply Tuesday, trading at about 2.605 percent from a high of 2.66. That set the tone for wide selling on the Nasdaq, which neared correction territory after Tuesday's morning trading session, Cashin said. The composite hit its lowest levels in 4½ months after a 1.44-percent decline, and the and Dow also saw losses.

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Cashin, UBS' director of floor operations at the New York Stock Exchange, said 10-year Treasury bonds serve as the "orchestra conductor" leading the selloff.

"In a Pavlovian fashion, equities are responding to it," Cashin said. "Earlier today, the yield on the 10 year was down 20 ticks and that had the first mile selling. As the rumors out of Ukraine began to build up, it dropped another 7 ticks and that gave us another leg down here."

—By CNBC's Jeff Morganteen.