After yields on the U.S. Treasury 10-year notes dipped below 2 percent for the first time since May 2013, a series of risks could push them even lower, one fixed-income expert said Wednesday.

"I don't think it's the U.S. economy," said Rick Rieder, BlackRock Chief Investment Officer of Fundamental Fixed Income. "We're pretty sanguine about U.S. growth."

Issues that impact yields include geopolitical risk, health-care concerns and crowded positions in the market, said Rieder, whose 10-year target for the yield on the 10-year bond was 2.50 to 2.60 percent.

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On CNBC's "," Rieder said he expected GDP to show 3 percent growth in the third quarter but saw other risks in the market.

"It's not the U.S.," he said. "It's what people are worried about. Is the leverage globally and you're not creating enough aggregate demand. And everybody's eyes are on (European Central Bank President) Mario Draghi, and can he solve this? It's very hard to do it with monetary policy."

China and Japan's economic performance were also factors, he added. "To predict that we're at the bottom of yields is pretty tough here, given all the event risk."

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Rieder also said there aren't enough safe-haven financial assets globally.

"There's a tremendous amount of exogenous influence that has taken place," he said. "We think yields are going to drift higher."